src/syscall/js/js_test.go - go - Git at Google

 // Copyright 2018 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // +build js,wasm

 // To run these tests:
 //
 // - Install Node
 // - Add /path/to/go/misc/wasm to your $PATH (so that "go test" can find
 //   "go_js_wasm_exec").
 // - GOOS=js GOARCH=wasm go test
 //
 // See -exec in "go help test", and "go help run" for details.

 package js_test

 import (
 	"fmt"
 	"math"
 	"syscall/js"
 	"testing"
 )

 var dummys = js.Global().Call("eval", `({
 	someBool: true,
 	someString: "abc\u1234",
 	someInt: 42,
 	someFloat: 42.123,
 	someArray: [41, 42, 43],
 	someDate: new Date(),
 	add: function(a, b) {
 		return a + b;
 	},
 	zero: 0,
 	stringZero: "0",
 	NaN: NaN,
 	emptyObj: {},
 	emptyArray: [],
 	Infinity: Infinity,
 	NegInfinity: -Infinity,
 	objNumber0: new Number(0),
 	objBooleanFalse: new Boolean(false),
 })`)

 func TestBool(t *testing.T) {
 	want := true
 	o := dummys.Get("someBool")
 	if got := o.Bool(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	dummys.Set("otherBool", want)
 	if got := dummys.Get("otherBool").Bool(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if dummys.Get("someBool") != dummys.Get("someBool") {
 		t.Errorf("same value not equal")
 	}
 }

 func TestString(t *testing.T) {
 	want := "abc\u1234"
 	o := dummys.Get("someString")
 	if got := o.String(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	dummys.Set("otherString", want)
 	if got := dummys.Get("otherString").String(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if dummys.Get("someString") != dummys.Get("someString") {
 		t.Errorf("same value not equal")
 	}

 	if got, want := js.Undefined().String(), "<undefined>"; got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if got, want := js.Null().String(), "<null>"; got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if got, want := js.ValueOf(true).String(), "<boolean: true>"; got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if got, want := js.ValueOf(42.5).String(), "<number: 42.5>"; got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if got, want := js.Global().Call("Symbol").String(), "<symbol>"; got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if got, want := js.Global().String(), "<object>"; got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if got, want := js.Global().Get("setTimeout").String(), "<function>"; got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 }

 func TestInt(t *testing.T) {
 	want := 42
 	o := dummys.Get("someInt")
 	if got := o.Int(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	dummys.Set("otherInt", want)
 	if got := dummys.Get("otherInt").Int(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if dummys.Get("someInt") != dummys.Get("someInt") {
 		t.Errorf("same value not equal")
 	}
 	if got := dummys.Get("zero").Int(); got != 0 {
 		t.Errorf("got %#v, want %#v", got, 0)
 	}
 }

 func TestIntConversion(t *testing.T) {
 	testIntConversion(t, 0)
 	testIntConversion(t, 1)
 	testIntConversion(t, -1)
 	testIntConversion(t, 1<<20)
 	testIntConversion(t, -1<<20)
 	testIntConversion(t, 1<<40)
 	testIntConversion(t, -1<<40)
 	testIntConversion(t, 1<<60)
 	testIntConversion(t, -1<<60)
 }

 func testIntConversion(t *testing.T, want int) {
 	if got := js.ValueOf(want).Int(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 }

 func TestFloat(t *testing.T) {
 	want := 42.123
 	o := dummys.Get("someFloat")
 	if got := o.Float(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	dummys.Set("otherFloat", want)
 	if got := dummys.Get("otherFloat").Float(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if dummys.Get("someFloat") != dummys.Get("someFloat") {
 		t.Errorf("same value not equal")
 	}
 }

 func TestObject(t *testing.T) {
 	if dummys.Get("someArray") != dummys.Get("someArray") {
 		t.Errorf("same value not equal")
 	}

 	// An object and its prototype should not be equal.
 	proto := js.Global().Get("Object").Get("prototype")
 	o := js.Global().Call("eval", "new Object()")
 	if proto == o {
 		t.Errorf("object equals to its prototype")
 	}
 }

 func TestFrozenObject(t *testing.T) {
 	o := js.Global().Call("eval", "(function () { let o = new Object(); o.field = 5; Object.freeze(o); return o; })()")
 	want := 5
 	if got := o.Get("field").Int(); want != got {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 }

 func TestNaN(t *testing.T) {
 	want := js.ValueOf(math.NaN())
 	got := dummys.Get("NaN")
 	if got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 }

 func TestUndefined(t *testing.T) {
 	dummys.Set("test", js.Undefined())
 	if dummys == js.Undefined() || dummys.Get("test") != js.Undefined() || dummys.Get("xyz") != js.Undefined() {
 		t.Errorf("js.Undefined expected")
 	}
 }

 func TestNull(t *testing.T) {
 	dummys.Set("test1", nil)
 	dummys.Set("test2", js.Null())
 	if dummys == js.Null() || dummys.Get("test1") != js.Null() || dummys.Get("test2") != js.Null() {
 		t.Errorf("js.Null expected")
 	}
 }

 func TestLength(t *testing.T) {
 	if got := dummys.Get("someArray").Length(); got != 3 {
 		t.Errorf("got %#v, want %#v", got, 3)
 	}
 }

 func TestGet(t *testing.T) {
 	// positive cases get tested per type

 	expectValueError(t, func() {
 		dummys.Get("zero").Get("badField")
 	})
 }

 func TestSet(t *testing.T) {
 	// positive cases get tested per type

 	expectValueError(t, func() {
 		dummys.Get("zero").Set("badField", 42)
 	})
 }

 func TestDelete(t *testing.T) {
 	dummys.Set("test", 42)
 	dummys.Delete("test")
 	if dummys.Call("hasOwnProperty", "test").Bool() {
 		t.Errorf("property still exists")
 	}

 	expectValueError(t, func() {
 		dummys.Get("zero").Delete("badField")
 	})
 }

 func TestIndex(t *testing.T) {
 	if got := dummys.Get("someArray").Index(1).Int(); got != 42 {
 		t.Errorf("got %#v, want %#v", got, 42)
 	}

 	expectValueError(t, func() {
 		dummys.Get("zero").Index(1)
 	})
 }

 func TestSetIndex(t *testing.T) {
 	dummys.Get("someArray").SetIndex(2, 99)
 	if got := dummys.Get("someArray").Index(2).Int(); got != 99 {
 		t.Errorf("got %#v, want %#v", got, 99)
 	}

 	expectValueError(t, func() {
 		dummys.Get("zero").SetIndex(2, 99)
 	})
 }

 func TestCall(t *testing.T) {
 	var i int64 = 40
 	if got := dummys.Call("add", i, 2).Int(); got != 42 {
 		t.Errorf("got %#v, want %#v", got, 42)
 	}
 	if got := dummys.Call("add", js.Global().Call("eval", "40"), 2).Int(); got != 42 {
 		t.Errorf("got %#v, want %#v", got, 42)
 	}

 	expectPanic(t, func() {
 		dummys.Call("zero")
 	})
 	expectValueError(t, func() {
 		dummys.Get("zero").Call("badMethod")
 	})
 }

 func TestInvoke(t *testing.T) {
 	var i int64 = 40
 	if got := dummys.Get("add").Invoke(i, 2).Int(); got != 42 {
 		t.Errorf("got %#v, want %#v", got, 42)
 	}

 	expectValueError(t, func() {
 		dummys.Get("zero").Invoke()
 	})
 }

 func TestNew(t *testing.T) {
 	if got := js.Global().Get("Array").New(42).Length(); got != 42 {
 		t.Errorf("got %#v, want %#v", got, 42)
 	}

 	expectValueError(t, func() {
 		dummys.Get("zero").New()
 	})
 }

 func TestInstanceOf(t *testing.T) {
 	someArray := js.Global().Get("Array").New()
 	if got, want := someArray.InstanceOf(js.Global().Get("Array")), true; got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if got, want := someArray.InstanceOf(js.Global().Get("Function")), false; got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 }

 func TestType(t *testing.T) {
 	if got, want := js.Undefined().Type(), js.TypeUndefined; got != want {
 		t.Errorf("got %s, want %s", got, want)
 	}
 	if got, want := js.Null().Type(), js.TypeNull; got != want {
 		t.Errorf("got %s, want %s", got, want)
 	}
 	if got, want := js.ValueOf(true).Type(), js.TypeBoolean; got != want {
 		t.Errorf("got %s, want %s", got, want)
 	}
 	if got, want := js.ValueOf(0).Type(), js.TypeNumber; got != want {
 		t.Errorf("got %s, want %s", got, want)
 	}
 	if got, want := js.ValueOf(42).Type(), js.TypeNumber; got != want {
 		t.Errorf("got %s, want %s", got, want)
 	}
 	if got, want := js.ValueOf("test").Type(), js.TypeString; got != want {
 		t.Errorf("got %s, want %s", got, want)
 	}
 	if got, want := js.Global().Get("Symbol").Invoke("test").Type(), js.TypeSymbol; got != want {
 		t.Errorf("got %s, want %s", got, want)
 	}
 	if got, want := js.Global().Get("Array").New().Type(), js.TypeObject; got != want {
 		t.Errorf("got %s, want %s", got, want)
 	}
 	if got, want := js.Global().Get("Array").Type(), js.TypeFunction; got != want {
 		t.Errorf("got %s, want %s", got, want)
 	}
 }

 type object = map[string]interface{}
 type array = []interface{}

 func TestValueOf(t *testing.T) {
 	a := js.ValueOf(array{0, array{0, 42, 0}, 0})
 	if got := a.Index(1).Index(1).Int(); got != 42 {
 		t.Errorf("got %v, want %v", got, 42)
 	}

 	o := js.ValueOf(object{"x": object{"y": 42}})
 	if got := o.Get("x").Get("y").Int(); got != 42 {
 		t.Errorf("got %v, want %v", got, 42)
 	}
 }

 func TestZeroValue(t *testing.T) {
 	var v js.Value
 	if v != js.Undefined() {
 		t.Error("zero js.Value is not js.Undefined()")
 	}
 }

 func TestFuncOf(t *testing.T) {
 	c := make(chan struct{})
 	cb := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 		if got := args[0].Int(); got != 42 {
 			t.Errorf("got %#v, want %#v", got, 42)
 		}
 		c <- struct{}{}
 		return nil
 	})
 	defer cb.Release()
 	js.Global().Call("setTimeout", cb, 0, 42)
 	<-c
 }

 func TestInvokeFunction(t *testing.T) {
 	called := false
 	cb := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 		cb2 := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 			called = true
 			return 42
 		})
 		defer cb2.Release()
 		return cb2.Invoke()
 	})
 	defer cb.Release()
 	if got := cb.Invoke().Int(); got != 42 {
 		t.Errorf("got %#v, want %#v", got, 42)
 	}
 	if !called {
 		t.Error("function not called")
 	}
 }

 func ExampleFuncOf() {
 	var cb js.Func
 	cb = js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 		fmt.Println("button clicked")
 		cb.Release() // release the function if the button will not be clicked again
 		return nil
 	})
 	js.Global().Get("document").Call("getElementById", "myButton").Call("addEventListener", "click", cb)
 }

 // See
 // - https://developer.mozilla.org/en-US/docs/Glossary/Truthy
 // - https://stackoverflow.com/questions/19839952/all-falsey-values-in-javascript/19839953#19839953
 // - http://www.ecma-international.org/ecma-262/5.1/#sec-9.2
 func TestTruthy(t *testing.T) {
 	want := true
 	for _, key := range []string{
 		"someBool", "someString", "someInt", "someFloat", "someArray", "someDate",
 		"stringZero", // "0" is truthy
 		"add",        // functions are truthy
 		"emptyObj", "emptyArray", "Infinity", "NegInfinity",
 		// All objects are truthy, even if they're Number(0) or Boolean(false).
 		"objNumber0", "objBooleanFalse",
 	} {
 		if got := dummys.Get(key).Truthy(); got != want {
 			t.Errorf("%s: got %#v, want %#v", key, got, want)
 		}
 	}

 	want = false
 	if got := dummys.Get("zero").Truthy(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if got := dummys.Get("NaN").Truthy(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if got := js.ValueOf("").Truthy(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if got := js.Null().Truthy(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 	if got := js.Undefined().Truthy(); got != want {
 		t.Errorf("got %#v, want %#v", got, want)
 	}
 }

 func expectValueError(t *testing.T, fn func()) {
 	defer func() {
 		err := recover()
 		if _, ok := err.(*js.ValueError); !ok {
 			t.Errorf("expected *js.ValueError, got %T", err)
 		}
 	}()
 	fn()
 }

 func expectPanic(t *testing.T, fn func()) {
 	defer func() {
 		err := recover()
 		if err == nil {
 			t.Errorf("expected panic")
 		}
 	}()
 	fn()
 }

 var copyTests = []struct {
 	srcLen  int
 	dstLen  int
 	copyLen int
 }{
 	{5, 3, 3},
 	{3, 5, 3},
 	{0, 0, 0},
 }

 func TestCopyBytesToGo(t *testing.T) {
 	for _, tt := range copyTests {
 		t.Run(fmt.Sprintf("%d-to-%d", tt.srcLen, tt.dstLen), func(t *testing.T) {
 			src := js.Global().Get("Uint8Array").New(tt.srcLen)
 			if tt.srcLen >= 2 {
 				src.SetIndex(1, 42)
 			}
 			dst := make([]byte, tt.dstLen)

 			if got, want := js.CopyBytesToGo(dst, src), tt.copyLen; got != want {
 				t.Errorf("copied %d, want %d", got, want)
 			}
 			if tt.dstLen >= 2 {
 				if got, want := int(dst[1]), 42; got != want {
 					t.Errorf("got %d, want %d", got, want)
 				}
 			}
 		})
 	}
 }

 func TestCopyBytesToJS(t *testing.T) {
 	for _, tt := range copyTests {
 		t.Run(fmt.Sprintf("%d-to-%d", tt.srcLen, tt.dstLen), func(t *testing.T) {
 			src := make([]byte, tt.srcLen)
 			if tt.srcLen >= 2 {
 				src[1] = 42
 			}
 			dst := js.Global().Get("Uint8Array").New(tt.dstLen)

 			if got, want := js.CopyBytesToJS(dst, src), tt.copyLen; got != want {
 				t.Errorf("copied %d, want %d", got, want)
 			}
 			if tt.dstLen >= 2 {
 				if got, want := dst.Index(1).Int(), 42; got != want {
 					t.Errorf("got %d, want %d", got, want)
 				}
 			}
 		})
 	}
 }

 // BenchmarkDOM is a simple benchmark which emulates a webapp making DOM operations.
 // It creates a div, and sets its id. Then searches by that id and sets some data.
 // Finally it removes that div.
 func BenchmarkDOM(b *testing.B) {
 	document := js.Global().Get("document")
 	if document == js.Undefined() {
 		b.Skip("Not a browser environment. Skipping.")
 	}
 	const data = "someString"
 	for i := 0; i < b.N; i++ {
 		div := document.Call("createElement", "div")
 		div.Call("setAttribute", "id", "myDiv")
 		document.Get("body").Call("appendChild", div)
 		myDiv := document.Call("getElementById", "myDiv")
 		myDiv.Set("innerHTML", data)

 		if got, want := myDiv.Get("innerHTML").String(), data; got != want {
 			b.Errorf("got %s, want %s", got, want)
 		}
 		document.Get("body").Call("removeChild", div)
 	}
 }
	// Copyright 2018 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	// +build js,wasm

	// To run these tests:
	//
	// - Install Node
	// - Add /path/to/go/misc/wasm to your $PATH (so that "go test" can find
	// "go_js_wasm_exec").
	// - GOOS=js GOARCH=wasm go test
	//
	// See -exec in "go help test", and "go help run" for details.

	package js_test

	import (
	"fmt"
	"math"
	"syscall/js"
	"testing"
	)

	var dummys = js.Global().Call("eval", `({
	someBool: true,
	someString: "abc\u1234",
	someInt: 42,
	someFloat: 42.123,
	someArray: [41, 42, 43],
	someDate: new Date(),
	add: function(a, b) {
	return a + b;
	},
	zero: 0,
	stringZero: "0",
	NaN: NaN,
	emptyObj: {},
	emptyArray: [],
	Infinity: Infinity,
	NegInfinity: -Infinity,
	objNumber0: new Number(0),
	objBooleanFalse: new Boolean(false),
	})`)

	func TestBool(t *testing.T) {
	want := true
	o := dummys.Get("someBool")
	if got := o.Bool(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	dummys.Set("otherBool", want)
	if got := dummys.Get("otherBool").Bool(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if dummys.Get("someBool") != dummys.Get("someBool") {
	t.Errorf("same value not equal")
	}
	}

	func TestString(t *testing.T) {
	want := "abc\u1234"
	o := dummys.Get("someString")
	if got := o.String(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	dummys.Set("otherString", want)
	if got := dummys.Get("otherString").String(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if dummys.Get("someString") != dummys.Get("someString") {
	t.Errorf("same value not equal")
	}

	if got, want := js.Undefined().String(), "<undefined>"; got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if got, want := js.Null().String(), "<null>"; got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if got, want := js.ValueOf(true).String(), "<boolean: true>"; got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if got, want := js.ValueOf(42.5).String(), "<number: 42.5>"; got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if got, want := js.Global().Call("Symbol").String(), "<symbol>"; got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if got, want := js.Global().String(), "<object>"; got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if got, want := js.Global().Get("setTimeout").String(), "<function>"; got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	}

	func TestInt(t *testing.T) {
	want := 42
	o := dummys.Get("someInt")
	if got := o.Int(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	dummys.Set("otherInt", want)
	if got := dummys.Get("otherInt").Int(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if dummys.Get("someInt") != dummys.Get("someInt") {
	t.Errorf("same value not equal")
	}
	if got := dummys.Get("zero").Int(); got != 0 {
	t.Errorf("got %#v, want %#v", got, 0)
	}
	}

	func TestIntConversion(t *testing.T) {
	testIntConversion(t, 0)
	testIntConversion(t, 1)
	testIntConversion(t, -1)
	testIntConversion(t, 1<<20)
	testIntConversion(t, -1<<20)
	testIntConversion(t, 1<<40)
	testIntConversion(t, -1<<40)
	testIntConversion(t, 1<<60)
	testIntConversion(t, -1<<60)
	}

	func testIntConversion(t *testing.T, want int) {
	if got := js.ValueOf(want).Int(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	}

	func TestFloat(t *testing.T) {
	want := 42.123
	o := dummys.Get("someFloat")
	if got := o.Float(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	dummys.Set("otherFloat", want)
	if got := dummys.Get("otherFloat").Float(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if dummys.Get("someFloat") != dummys.Get("someFloat") {
	t.Errorf("same value not equal")
	}
	}

	func TestObject(t *testing.T) {
	if dummys.Get("someArray") != dummys.Get("someArray") {
	t.Errorf("same value not equal")
	}

	// An object and its prototype should not be equal.
	proto := js.Global().Get("Object").Get("prototype")
	o := js.Global().Call("eval", "new Object()")
	if proto == o {
	t.Errorf("object equals to its prototype")
	}
	}

	func TestFrozenObject(t *testing.T) {
	o := js.Global().Call("eval", "(function () { let o = new Object(); o.field = 5; Object.freeze(o); return o; })()")
	want := 5
	if got := o.Get("field").Int(); want != got {
	t.Errorf("got %#v, want %#v", got, want)
	}
	}

	func TestNaN(t *testing.T) {
	want := js.ValueOf(math.NaN())
	got := dummys.Get("NaN")
	if got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	}

	func TestUndefined(t *testing.T) {
	dummys.Set("test", js.Undefined())
	if dummys == js.Undefined() \|\| dummys.Get("test") != js.Undefined() \|\| dummys.Get("xyz") != js.Undefined() {
	t.Errorf("js.Undefined expected")
	}
	}

	func TestNull(t *testing.T) {
	dummys.Set("test1", nil)
	dummys.Set("test2", js.Null())
	if dummys == js.Null() \|\| dummys.Get("test1") != js.Null() \|\| dummys.Get("test2") != js.Null() {
	t.Errorf("js.Null expected")
	}
	}

	func TestLength(t *testing.T) {
	if got := dummys.Get("someArray").Length(); got != 3 {
	t.Errorf("got %#v, want %#v", got, 3)
	}
	}

	func TestGet(t *testing.T) {
	// positive cases get tested per type

	expectValueError(t, func() {
	dummys.Get("zero").Get("badField")
	})
	}

	func TestSet(t *testing.T) {
	// positive cases get tested per type

	expectValueError(t, func() {
	dummys.Get("zero").Set("badField", 42)
	})
	}

	func TestDelete(t *testing.T) {
	dummys.Set("test", 42)
	dummys.Delete("test")
	if dummys.Call("hasOwnProperty", "test").Bool() {
	t.Errorf("property still exists")
	}

	expectValueError(t, func() {
	dummys.Get("zero").Delete("badField")
	})
	}

	func TestIndex(t *testing.T) {
	if got := dummys.Get("someArray").Index(1).Int(); got != 42 {
	t.Errorf("got %#v, want %#v", got, 42)
	}

	expectValueError(t, func() {
	dummys.Get("zero").Index(1)
	})
	}

	func TestSetIndex(t *testing.T) {
	dummys.Get("someArray").SetIndex(2, 99)
	if got := dummys.Get("someArray").Index(2).Int(); got != 99 {
	t.Errorf("got %#v, want %#v", got, 99)
	}

	expectValueError(t, func() {
	dummys.Get("zero").SetIndex(2, 99)
	})
	}

	func TestCall(t *testing.T) {
	var i int64 = 40
	if got := dummys.Call("add", i, 2).Int(); got != 42 {
	t.Errorf("got %#v, want %#v", got, 42)
	}
	if got := dummys.Call("add", js.Global().Call("eval", "40"), 2).Int(); got != 42 {
	t.Errorf("got %#v, want %#v", got, 42)
	}

	expectPanic(t, func() {
	dummys.Call("zero")
	})
	expectValueError(t, func() {
	dummys.Get("zero").Call("badMethod")
	})
	}

	func TestInvoke(t *testing.T) {
	var i int64 = 40
	if got := dummys.Get("add").Invoke(i, 2).Int(); got != 42 {
	t.Errorf("got %#v, want %#v", got, 42)
	}

	expectValueError(t, func() {
	dummys.Get("zero").Invoke()
	})
	}

	func TestNew(t *testing.T) {
	if got := js.Global().Get("Array").New(42).Length(); got != 42 {
	t.Errorf("got %#v, want %#v", got, 42)
	}

	expectValueError(t, func() {
	dummys.Get("zero").New()
	})
	}

	func TestInstanceOf(t *testing.T) {
	someArray := js.Global().Get("Array").New()
	if got, want := someArray.InstanceOf(js.Global().Get("Array")), true; got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if got, want := someArray.InstanceOf(js.Global().Get("Function")), false; got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	}

	func TestType(t *testing.T) {
	if got, want := js.Undefined().Type(), js.TypeUndefined; got != want {
	t.Errorf("got %s, want %s", got, want)
	}
	if got, want := js.Null().Type(), js.TypeNull; got != want {
	t.Errorf("got %s, want %s", got, want)
	}
	if got, want := js.ValueOf(true).Type(), js.TypeBoolean; got != want {
	t.Errorf("got %s, want %s", got, want)
	}
	if got, want := js.ValueOf(0).Type(), js.TypeNumber; got != want {
	t.Errorf("got %s, want %s", got, want)
	}
	if got, want := js.ValueOf(42).Type(), js.TypeNumber; got != want {
	t.Errorf("got %s, want %s", got, want)
	}
	if got, want := js.ValueOf("test").Type(), js.TypeString; got != want {
	t.Errorf("got %s, want %s", got, want)
	}
	if got, want := js.Global().Get("Symbol").Invoke("test").Type(), js.TypeSymbol; got != want {
	t.Errorf("got %s, want %s", got, want)
	}
	if got, want := js.Global().Get("Array").New().Type(), js.TypeObject; got != want {
	t.Errorf("got %s, want %s", got, want)
	}
	if got, want := js.Global().Get("Array").Type(), js.TypeFunction; got != want {
	t.Errorf("got %s, want %s", got, want)
	}
	}

	type object = map[string]interface{}
	type array = []interface{}

	func TestValueOf(t *testing.T) {
	a := js.ValueOf(array{0, array{0, 42, 0}, 0})
	if got := a.Index(1).Index(1).Int(); got != 42 {
	t.Errorf("got %v, want %v", got, 42)
	}

	o := js.ValueOf(object{"x": object{"y": 42}})
	if got := o.Get("x").Get("y").Int(); got != 42 {
	t.Errorf("got %v, want %v", got, 42)
	}
	}

	func TestZeroValue(t *testing.T) {
	var v js.Value
	if v != js.Undefined() {
	t.Error("zero js.Value is not js.Undefined()")
	}
	}

	func TestFuncOf(t *testing.T) {
	c := make(chan struct{})
	cb := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
	if got := args[0].Int(); got != 42 {
	t.Errorf("got %#v, want %#v", got, 42)
	}
	c <- struct{}{}
	return nil
	})
	defer cb.Release()
	js.Global().Call("setTimeout", cb, 0, 42)
	<-c
	}

	func TestInvokeFunction(t *testing.T) {
	called := false
	cb := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
	cb2 := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
	called = true
	return 42
	})
	defer cb2.Release()
	return cb2.Invoke()
	})
	defer cb.Release()
	if got := cb.Invoke().Int(); got != 42 {
	t.Errorf("got %#v, want %#v", got, 42)
	}
	if !called {
	t.Error("function not called")
	}
	}

	func ExampleFuncOf() {
	var cb js.Func
	cb = js.FuncOf(func(this js.Value, args []js.Value) interface{} {
	fmt.Println("button clicked")
	cb.Release() // release the function if the button will not be clicked again
	return nil
	})
	js.Global().Get("document").Call("getElementById", "myButton").Call("addEventListener", "click", cb)
	}

	// See
	// - https://developer.mozilla.org/en-US/docs/Glossary/Truthy
	// - https://stackoverflow.com/questions/19839952/all-falsey-values-in-javascript/19839953#19839953
	// - http://www.ecma-international.org/ecma-262/5.1/#sec-9.2
	func TestTruthy(t *testing.T) {
	want := true
	for _, key := range []string{
	"someBool", "someString", "someInt", "someFloat", "someArray", "someDate",
	"stringZero", // "0" is truthy
	"add", // functions are truthy
	"emptyObj", "emptyArray", "Infinity", "NegInfinity",
	// All objects are truthy, even if they're Number(0) or Boolean(false).
	"objNumber0", "objBooleanFalse",
	} {
	if got := dummys.Get(key).Truthy(); got != want {
	t.Errorf("%s: got %#v, want %#v", key, got, want)
	}
	}

	want = false
	if got := dummys.Get("zero").Truthy(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if got := dummys.Get("NaN").Truthy(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if got := js.ValueOf("").Truthy(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if got := js.Null().Truthy(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	if got := js.Undefined().Truthy(); got != want {
	t.Errorf("got %#v, want %#v", got, want)
	}
	}

	func expectValueError(t *testing.T, fn func()) {
	defer func() {
	err := recover()
	if _, ok := err.(*js.ValueError); !ok {
	t.Errorf("expected *js.ValueError, got %T", err)
	}
	}()
	fn()
	}

	func expectPanic(t *testing.T, fn func()) {
	defer func() {
	err := recover()
	if err == nil {
	t.Errorf("expected panic")
	}
	}()
	fn()
	}

	var copyTests = []struct {
	srcLen int
	dstLen int
	copyLen int
	}{
	{5, 3, 3},
	{3, 5, 3},
	{0, 0, 0},
	}

	func TestCopyBytesToGo(t *testing.T) {
	for _, tt := range copyTests {
	t.Run(fmt.Sprintf("%d-to-%d", tt.srcLen, tt.dstLen), func(t *testing.T) {
	src := js.Global().Get("Uint8Array").New(tt.srcLen)
	if tt.srcLen >= 2 {
	src.SetIndex(1, 42)
	}
	dst := make([]byte, tt.dstLen)

	if got, want := js.CopyBytesToGo(dst, src), tt.copyLen; got != want {
	t.Errorf("copied %d, want %d", got, want)
	}
	if tt.dstLen >= 2 {
	if got, want := int(dst[1]), 42; got != want {
	t.Errorf("got %d, want %d", got, want)
	}
	}
	})
	}
	}

	func TestCopyBytesToJS(t *testing.T) {
	for _, tt := range copyTests {
	t.Run(fmt.Sprintf("%d-to-%d", tt.srcLen, tt.dstLen), func(t *testing.T) {
	src := make([]byte, tt.srcLen)
	if tt.srcLen >= 2 {
	src[1] = 42
	}
	dst := js.Global().Get("Uint8Array").New(tt.dstLen)

	if got, want := js.CopyBytesToJS(dst, src), tt.copyLen; got != want {
	t.Errorf("copied %d, want %d", got, want)
	}
	if tt.dstLen >= 2 {
	if got, want := dst.Index(1).Int(), 42; got != want {
	t.Errorf("got %d, want %d", got, want)
	}
	}
	})
	}
	}

	// BenchmarkDOM is a simple benchmark which emulates a webapp making DOM operations.
	// It creates a div, and sets its id. Then searches by that id and sets some data.
	// Finally it removes that div.
	func BenchmarkDOM(b *testing.B) {
	document := js.Global().Get("document")
	if document == js.Undefined() {
	b.Skip("Not a browser environment. Skipping.")
	}
	const data = "someString"
	for i := 0; i < b.N; i++ {
	div := document.Call("createElement", "div")
	div.Call("setAttribute", "id", "myDiv")
	document.Get("body").Call("appendChild", div)
	myDiv := document.Call("getElementById", "myDiv")
	myDiv.Set("innerHTML", data)

	if got, want := myDiv.Get("innerHTML").String(), data; got != want {
	b.Errorf("got %s, want %s", got, want)
	}
	document.Get("body").Call("removeChild", div)
	}
	}