@babel/plugin-transform-arrow-functions

    In

    Out

    1. var a = function() {};
    2. var a = function(b) {
    3.   return b;
    4. };
    6. const double = [1, 2, 3].map(function(num) {
    7.   return num * 2;
    8. });
    9. console.log(double); // [2,4,6]
    11. var bob = {
    12.   _name: "Bob",
    13.   _friends: ["Sally", "Tom"],
    14.   printFriends() {
    16.     this._friends.forEach(function(f) {
    17.       return console.log(_this._name + " knows " + f);
    18.     });
    19.   },
    21. console.log(bob.printFriends());

    Without options:

    1. {
    2.   "plugins": ["@babel/plugin-transform-arrow-functions"]
    3. }
    1. babel --plugins @babel/plugin-transform-arrow-functions script.js

    boolean, defaults to false.

    Example

    Using spec mode with the above example produces:

    1. var _this = this;
    3. var a = function a() {
    4.   babelHelpers.newArrowCheck(this, _this);
    5. }.bind(this);
    6. var a = function a(b) {
    7.   babelHelpers.newArrowCheck(this, _this);
    8.   return b;
    9. }.bind(this);
    11. const double = [1, 2, 3].map(
    12.     babelHelpers.newArrowCheck(this, _this);
    14.   }.bind(this)
    15. );
    16. console.log(double); // [2,4,6]
    18. var bob = {
    19.   _name: "Bob",
    20.   _friends: ["Sally", "Tom"],
    21.   printFriends() {
    22.     var _this2 = this;
    24.     this._friends.forEach(
    25.       function(f) {
    26.         babelHelpers.newArrowCheck(this, _this2);
    27.         return console.log(this._name + " knows " + f);
    28.       }.bind(this)
    29.     );
    30.   },
    31. };
    32. console.log(bob.printFriends());

    • Wrap the generated function in .bind(this) and keeps uses of this inside the function as-is, instead of using a renamed .

    • Add names to arrow functions.