call 和 apply 和有什么不一样?

问题描述

使用 Function.prototype.apply() 和 Function.prototype.call() 调用函数有什么区别?

What is the difference between using Function.prototype.apply() and Function.prototype.call() to invoke a function?

var func = function() {
  alert('hello!');
};

func.apply(); vs func.call();

上述两种方法之间是否存在性能差异?什么时候最好使用 call 而不是 apply，反之亦然?

Are there performance differences between the two aforementioned methods? When is it best to use call over apply and vice versa?

推荐答案

区别在于 apply 可以让你使用 arguments 作为数组来调用函数；call 需要明确列出参数.一个有用的助记符是A代表array，C代表comma."

The difference is that apply lets you invoke the function with arguments as an array; call requires the parameters be listed explicitly. A useful mnemonic is "A for array and C for comma."

请参阅 MDN 关于应用 和 调用.

See MDN's documentation on apply and call.

伪语法:

theFunction.apply(valueForThis, arrayOfArgs)

theFunction.call(valueForThis, arg1, arg2, ...)

从 ES6 开始，还有可能 spread数组与call函数一起使用，可以看到兼容性这里.

There is also, as of ES6, the possibility to spread the array for use with the call function, you can see the compatibilities here.

示例代码:

function theFunction(name, profession) {
    console.log("My name is " + name + " and I am a " + profession +".");
}
theFunction("John", "fireman");
theFunction.apply(undefined, ["Susan", "school teacher"]);
theFunction.call(undefined, "Claude", "mathematician");
theFunction.call(undefined, ...["Matthew", "physicist"]); // used with the spread operator

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