@babel/plugin-transform-parameters

    This plugin transforms ES2015 parameters to ES5, this includes:

    • Destructuring parameters
    • Default parameters
    • Rest parameters

    In

    1. function test() {
    2.   var x =
    3.   var _ref = arguments[1];
    4.   var a = _ref.a,
    5.     b = _ref.b;
    7.   for (
    8.     var _len = arguments.length,
    9.       args = Array(_len > 2 ? _len - 2 : 0),
    10.       _key = 2;
    12.     _key++
    13.   ) {
    14.     args[_key - 2] = arguments[_key];
    15.   }
    17. }

    Default parameters desugar into let declarations to retain proper semantics. If this is not supported in your environment then you’ll need the @babel/plugin-transform-block-scoping plugin.

    1. {
    2.   "plugins": ["@babel/plugin-transform-parameters"]
    3. }
    1. require("@babel/core").transformSync("code", {
    3. });

    boolean, defaults to false.

    Under the ignoreFunctionLength assumption, Babel will generate 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.

    1. // Spec behavior
    2. function bar1(arg1 = 1) {}
    3. bar1.length; // 0
    5. // ignoreFunctionLength: true
    6. function bar1(arg1 = 1) {}