javascript - 保存上下文

Question

我发现了一些有趣的问题。任务是对所有子函数进行包装，这将延迟实现。

function someFunc() {
  console.log(this.someProp);
}

var obj1 = {
  someProp: 1,
  method1: someFunc,
};

var obj2 = {
  someProp: 2,
  method2: someFunc,
};
Function.prototype.defer = function(ms) {
  let self = this;
  setTimeout(self, ms) //<<-- lose context(obj1, obj2)
};
obj1.method1(); // 1
obj2.method2(); // 2
obj1.method1.defer(1000); // 1 after 1 sec, now is undefined
obj2.method2.defer(1000); // 2 after 1 sec, now is undefined

标签： javascriptthisprototype

Answer 1

尝试使用 bind. 允许设置在调用函数或方法时bind()将绑定到哪个特定对象。this

function someFunc() {
  console.log(this.someProp);
}

var obj1 = {
  someProp: 1,
  method1: someFunc,
};

var obj2 = {
  someProp: 2,
  method2: someFunc,
};
Function.prototype.defer = function(ms) {
  setTimeout(this, ms) //<<-- lose context(obj1, obj2)
};
obj1.method1(); // 1
obj2.method2(); // 2
obj1.method1.bind(obj1).defer(1000); // 1 after 1 sec, now is undefined
obj2.method2.bind(obj2).defer(1000); // 2 after 1 sec, now is undefined