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测试通过 #147

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测试通过 #147

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16 changes: 12 additions & 4 deletions test/test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,8 @@ describe('this', function () {
say: function () {
setTimeout(() => {
// this 是什么？想想为什么？
this.should.equal(null)
// this 是 obj, 箭头函数中的this是在定义函数的时候绑定，而不是在执行函数时绑定
this.should.equal(obj)
done()
}, 0)
}
Expand All @@ -15,7 +16,8 @@ describe('this', function () {
it('global', function () {
function test() {
// this 是什么？想想为什么？
this.should.equal(null)
// this使用默认绑定（非严格模式），严格模式是undefined
this.should.equal(global)
}
test()
})
Expand All @@ -26,8 +28,13 @@ describe('this', function () {
say: function () {
function _say() {
// this 是什么？想想为什么？
this.should.equal(null)
// 《你不知道的js上》书中 96 页 2.4.1 被忽略的this，
// 如果你把null或者undefined作为this的绑定对象传如call，apply或者bind，
// 这些值在调用时会被忽略，实际使用的是默认绑定规则
// 显示绑定了obj，但是此时 obj 是 undefined, 所以 this 是 global（非严格模式），严格模式是undefined
this.should.equal(global)
}
console.log('obj:', obj)
return _say.bind(obj)
}()
}
Expand All @@ -39,7 +46,8 @@ describe('this', function () {
obj.say = function () {
function _say() {
// this 是什么？想想为什么？
this.should.equal(null)
// this 是 obj，同上一个，因为此时的obj已存在
this.should.equal(obj)
}
return _say.bind(obj)
}()
Expand Down