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检测函数是否通过new运算符被调用的三种方法 #20

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OPY-bbt opened this issue Nov 23, 2019 · 0 comments

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OPY-bbt commented Nov 23, 2019 •

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利用严格模式下，函数中this指向undefined，直接调用会报错

function Parent() {
  "use strict";
  this.name = "rss";
}

instanceof 判断this

function Parent() {
  if (!(this instanceof Parent)) { throw new Error();}
}

new.target(使用new方法调用时，指向构造函数，普通函数调用指向 undefined)

function Parent() {
  if (new.target !== Parent) { throw new Error();}
}

OPY-bbt added the javascript label

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