fcdfc61bdb
* centralize plugin options * Centralize plugins options - move more options to the top - move validations that depend on options to the top * use isLoose option * Move more validations to the top * Move ref parameter for rewriteModuleStatementsAndPrepareHeader() to the top * fix eslint errors * remove unused parameter * set default systemGlobal value * Revert "Move ref parameter for rewriteModuleStatementsAndPrepareHeader() to the top" This reverts commit b3855302d17fa19d8acb4c8accab3680c8d2710e. * Revert "Move more validations to the top" This reverts commit e5861d8a034ff8f553391f55654f753bcf428a5d. * fix allowMutablePropsOnTags option usage * improve naming * change Contructor definition for sake of consistency * move allowMutablePropsOnTags validation to the top * add missing !
babel-plugin-transform-es2015-parameters
Compile ES2015 default and rest parameters to ES5
This plugin transforms ES2015 parameters to ES5, this includes:
- Destructuring parameters
- Default parameters
- Rest parameters
Examples
In
function test(x = "hello", { a, b }, ...args) {
console.log(x, a, b, args);
}
Out
function test() {
var x = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : "hello";
var _ref = arguments[1];
var a = _ref.a,
b = _ref.b;
for (var _len = arguments.length, args = Array(_len > 2 ? _len - 2 : 0), _key = 2; _key < _len; _key++) {
args[_key - 2] = arguments[_key];
}
console.log(x, a, b, args);
}
Installation
npm install --save-dev babel-plugin-transform-es2015-parameters
Caveats
Default parameters desugar into let declarations to retain proper semantics. If this is
not supported in your environment then you'll need the
transform-block-scoping plugin.
Usage
Via .babelrc (Recommended)
.babelrc
{
"plugins": ["transform-es2015-parameters"]
}
Via CLI
babel --plugins transform-es2015-parameters script.js
Via Node API
require("babel-core").transform("code", {
plugins: ["transform-es2015-parameters"]
});
Options
loose
boolean, defaults to false.
In loose mode, parameters with default values will be counted into the arity of the function. This is not spec behavior where these parameters do not add to function arity.
The loose implementation is a more performant solution as JavaScript engines will fully optimize a function that doesn't reference arguments. Please do your own benchmarking and determine if this option is the right fit for your application.
// Spec behavior
function bar1 (arg1 = 1) {}
bar1.length // 0
// Loose mode
function bar1 (arg1 = 1) {}
bar1.length // 1