javascript，promises，如何在 then 范围内访问变量 this
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javascript, promises, how to access variable this inside a then scope
提问by GWorking
I want to be able to call a function inside the .thenscope, and for that I use the this.foo()manner. But if I do this inside the .thenI get an error, since thisappears to be lost. What can I do?
我希望能够调用内部的功能。那么范围，为此，我用的是this.foo（）的方式。但是，如果我在.then 中执行此操作，则会出现错误，因为这似乎丢失了。我能做什么？
In this code, this would be equivalent to have the same output for the object this
在这段代码中，这相当于对this对象具有相同的输出
console.log(this)
one().then(function() {
console.log(this)
})
function one() {
var deferred = $q.defer();
deferred.resolve()
return deferred.promise;
}
This neither seems to work
这似乎都不起作用
console.log(this)
var a = this;
one().then(function(a) {
console.log(a)
})
回答by Andy
Your second code example is the right way to go. Because the scope changes in the new function, thischanges too, so you're right to make a reference to thisoutside of the function.
您的第二个代码示例是正确的方法。因为作用域在新函数中this发生了变化，也会发生变化，所以您this对函数外部进行引用是正确的。
The reason it failed is because the function is using athat you passed into the function rather than the global ayou defined outside it.
它失败的原因是因为该函数正在使用a您传递给该函数的函数，而不是a您在函数外部定义的全局变量。
In other words:
换句话说：
var a = this;
one().then(function () {
console.log(a)
});
