JavaScript中call与apply的区别

流楚丶格念 2021-07-20 03:52:32
javascript


一 定义:
function log (...args) {
console.log(...args)
}
function log () {
console.log.apply(console, arguments)
}
log(1, 2, 3)
log.bind()

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1. call()

  • 定义:调用一个对象的一个方法,以另一个对象替换当前对象。

  • 调用call的对象必须是个函数function

  • call的第一个参数将会是function改变上下文后指向的对象,如果不传,将会默认是全局对象window

  • 第二个参数开始可以接收任意个参数,这些参数将会作为function的参数传入function

2. apply()

  • 定义:应用某一对象的一个方法,用另一个对象替换当前对象。

  • 与call方法的使用基本一致,但是只接收两个参数,其中第二个参数必须是一个数组或者类数组,这也是这两个方法很重要的一个区别

二 异同

1. 相同点

  • 都能够改变方法的执行上下文(执行环境),将一个对象的方法交给另一个对象来执行,并且是立即执行

2. 不同点

  • call方法:从第二个参数开始可以接收任意个参数,每个参数会映射到相应位置的function的参数上,可以通过参数名调用,但是如果将所有的参数作为数组传入,它们会作为一个整体映射到function对应的第一个参数上,之后参数都为空

  • apply方法:最多只有两个参数,第二个参数接收数组或者类数组,但是都会被转换成类数组传入function中,并且会被映射到function对应的参数上

  • 更简单地说,apply和call功能一样,只是传入的参数列表形式不同:

    如 function.call(function1,var1,var2,var3)对应的apply写法为:function.apply(function1,[var1,var2,var3])

三 两个方法该如何选择?
  1. 根据你要传入的参数来做选择,不需要传参或者只有1个参数的时候,用call,当要传入多个对象时,用apply。

  2. 如果需要传入的参数已经是一个数组或者类数组了,就用apply,如果还是单独的需要逐个传入的,可以考虑使用call(如果你不嫌麻烦的话 )

版权声明
本文为[流楚丶格念]所创,转载请带上原文链接,感谢
https://blog.51cto.com/u_15265965/2891981

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