81811bf1b9
* Fix transform-arrow-functions in { spec: true } shadowing
The function name matching the variable declaration name could
shadow the actual function object inside the generated function,
leading to invalid behavior due to holding a reference to the
original unbound function.
* Combine it with transform-function-name just to be sure in spec: false
* Revert "Fix transform-arrow-functions in { spec: true } shadowing"
This reverts commit 1cafe2561d0b0ddd181b956a85eb074621da12e8.
* Much simpler version of the above fix
* Missing fixture updates
* Avoid using rest/spread to make the tests pass on node 4
* ...actually update _all_ the fixtures
@babel/plugin-transform-arrow-functions
Compile ES2015 arrow functions to ES5
Example
In
var a = () => {};
var a = (b) => b;
const double = [1,2,3].map((num) => num * 2);
console.log(double); // [2,4,6]
var bob = {
_name: "Bob",
_friends: ["Sally", "Tom"],
printFriends() {
this._friends.forEach(f =>
console.log(this._name + " knows " + f));
}
};
console.log(bob.printFriends());
Out
var a = function () {};
var a = function (b) {
return b;
};
const double = [1, 2, 3].map(function (num) {
return num * 2;
});
console.log(double); // [2,4,6]
var bob = {
_name: "Bob",
_friends: ["Sally", "Tom"],
printFriends() {
var _this = this;
this._friends.forEach(function (f) {
return console.log(_this._name + " knows " + f);
});
}
};
console.log(bob.printFriends());
Installation
npm install --save-dev @babel/plugin-transform-arrow-functions
Usage
Via .babelrc (Recommended)
.babelrc
Without options:
{
"plugins": ["@babel/transform-arrow-functions"]
}
With options:
{
"plugins": [
["@babel/transform-arrow-functions", { "spec": true }]
]
}
Via CLI
babel --plugins @babel/transform-arrow-functions script.js
Via Node API
require("@babel/core").transform("code", {
plugins: ["@babel/transform-arrow-functions"]
});
Options
spec
boolean, defaults to false.
Example
Using spec mode with the above example produces:
var _this = this;
var a = function a() {
babelHelpers.newArrowCheck(this, _this);
}.bind(this);
var a = function a(b) {
babelHelpers.newArrowCheck(this, _this);
return b;
}.bind(this);
const double = [1, 2, 3].map(function (num) {
babelHelpers.newArrowCheck(this, _this);
return num * 2;
}.bind(this));
console.log(double); // [2,4,6]
var bob = {
_name: "Bob",
_friends: ["Sally", "Tom"],
printFriends() {
var _this2 = this;
this._friends.forEach(function (f) {
babelHelpers.newArrowCheck(this, _this2);
return console.log(this._name + " knows " + f);
}.bind(this));
}
};
console.log(bob.printFriends());
This option enables the following:
-
Wrap the generated function in
.bind(this)and keeps uses ofthisinside the function as-is, instead of using a renamedthis. -
Add a runtime check to ensure the functions are not instantiated.
-
Add names to arrow functions.