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zhangke-exercise4 #142

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12 changes: 8 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)
// 箭头函数由于没有自己的this，所以内部的this就是外层代码块的this，因此这块的this指向最外一层的作用域环境
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指向为调用它的对象,test()为全局调用函数，如果是nodejs那么全局是global，浏览器在严格模式下为undefined
this.should.equal(undefined)
}
test()
})
Expand All @@ -26,7 +28,8 @@ describe('this', function () {
say: function () {
function _say() {
// this 是什么？想想为什么？
this.should.equal(null)
// bind改变this的指向为obj但是obj声明了没有赋值，所以this的指向为undefined
this.should.equal(undefined)
}
return _say.bind(obj)
}()
Expand All @@ -39,7 +42,8 @@ describe('this', function () {
obj.say = function () {
function _say() {
// this 是什么？想想为什么？
this.should.equal(null)
// bind修改了this的指向为obj
this.should.equal(obj)
}
return _say.bind(obj)
}()
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