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Babel 会将箭头函数编译成什么？ #46

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hanyueqiang opened this issue Apr 9, 2021 · 0 comments

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hanyueqiang commented Apr 9, 2021

babel会直接将箭头函数编译为普通函数,用到到this的地方会在箭头函数定义的作用域头部将this赋值给_this

编译箭头函数babel

@babel/plugin-transform-arrow-functions

示例

var a = (b) => b;

const double = [1,2,3].map((num) => num * 2);

var bob = {
  _name: "Bob",
  _friends: ["Sally", "Tom"],
  printFriends() {
    this._friends.forEach(f =>
      console.log(this._name + " knows " + f));
  }
};

编译后

var a = function (b) {
  return b;
};

const double = [1, 2, 3].map(function (num) {
  return num * 2;
});

var bob = {
  _name: "Bob",
  _friends: ["Sally", "Tom"],
  printFriends() {
    var _this = this;

    this._friends.forEach(function (f) {
      return console.log(_this._name + " knows " + f);
    });
  }
};

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