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6.19.0 Released

· 4 min read
Henry Zhu

object-rest-spread works standalone and a few new plugin options APIs were added!

v6.19.0 Summary (2016-11-16)​

🚀 New Feature​

#4755 Make object-rest-spread work as an independent plugin. (@hzoo)

This rewrite fixes a long standing issue where the object-rest-spread plugin was depending on 2 other plugins to compile RestProperty properly.

This fix important given the assumption that plugins should be independent and is vital for the use of babel-preset-env since new environments support destructuring natively.

In

JavaScript
const { a, ...b } = c;

Out

JavaScript
const { a } = c; // remove the `...b`
const b = _objectWithoutProperties(c, ["a"]); // use the helper

It's interesting to see all the places where you can destructure!

RestProperty

function a({ b, ...c }) {} // Parameters
JavaScript
const { a, ...b } = c; // VariableDeclaration
JavaScript
export var { a, ...b } = c; // ExportNamedDeclaration
JavaScript
try {} catch ({a, ...b}) {} // CatchClause
JavaScript
({a, ...b} = c); // AssignmentExpression
JavaScript
for ({a, ...b} of []) {} // ForXStatement

SpreadProperty

JavaScript
var a = { ...b, ...c } // ObjectExpression

#4544 Add the spec option to "transform-class-properties". (@motiz88)

Class properties will use Object.defineProperty instead of a simple this.x = y. Static fields are will use value: undefined even if they are not initialized.

Usage

JavaScript
{
  "plugins": [
    ["transform-class-properties", {
      "spec": true
    }]
  ]
}

In

JavaScript
class Foo {
  static bar;
  baz = 'guy';
}

Out

JavaScript
var Foo = function Foo() {
  _classCallCheck(this, Foo);
  this.baz = 'guy';
};

Out w/ "spec": true

JavaScript
var Foo = function Foo() {
  babelHelpers.classCallCheck(this, Foo);
  _initialiseProps.call(this);
};

Object.defineProperty(Foo, "bar", {
  enumerable: true,
  writable: true,
  value: undefined
});

var _initialiseProps = function () {
  Object.defineProperty(this, "bar", {
    enumerable: true,
    writable: true,
    value: foo
  });
};

#4836 Add path utilities path.isAncestor and path.isDescendant. (@boopathi)

We've added 2 similar "ancestry" path methods to path.findParent:

Usage

JavaScript
let programPath, numberPath;
traverse(ast, {
  Program(path) { programPath = path; },
  NumberPath(path) { numberPath = path; },
});

programPath.isAncestor(numberPath); // true
numberPath.isDescendant(programPath); // true

#4835 Add clearCache and clearPath as separate APIs under traverse. (@boopathi)

Usage

JavaScript
traverse.clearCache(); // clears both path's and scope cache
traverse.clearCache.clearPath();
traverse.clearCache.clearScope();

#4827 Add jsonCompatibleStrings option to babel-generator. (@kangax)

Usage

JavaScript
{
  "generatorOpts": {
    "jsonCompatibleStrings": true // defaults to false
  }
}

Set to true for the generator to use jsesc with "json": true. This will make it print "\u00A9" vs. "©";

#3547 Added flowCommaSeparator to babel-generator. (@sampepose)

Usage

JavaScript
{
  "generatorOpts": {
    "flowCommaSeparator": true // defaults to false
  }
}

Currently there are 2 supported syntaxes (, and ;) in Flow Object Types. The use of commas is in line with the more popular style and matches how objects are defined in JavaScript, making it a bit more natural to write.

JavaScript
var a: { param1: number; param2: string }
var a: { param1: number, param2: string }

#3553 Add t.isNodesEquivalent. (@hzoo)

Usage

JavaScript
assert(t.isNodesEquivalent(parse("1 + 1"), parse("1+1")) === true);

#4789 Support stage-2 import() as contextual import in transform-es2015-modules-systemjs. (@guybedford)

You'll want to add the stage-2 preset or explicitly include babel-plugin-syntax-dynamic-import (not enabled by default).

JavaScript
export function lazyLoadOperation () {
  return import('./x')
  .then(function (x) {
    x.y();
  });
}

🐛 Bug Fixes​

#4830 Will print the shorter of the NumericLiterals if using the minified option. (@shinew)

Input

JavaScript
5e1;
5e4;

Output

JavaScript
50;
5e4;

#4832 Fix transform-es2015-modules-systemjs to ensure consistent modules iteration. (@guybedford)

JavaScript
import "2"; // should be imported first
import "1"; // second

#4813 Fix binding kind of destructured variables relating to transform-react-constant-elements (@STRML)

Fixes an issue with destructuring parameters being hoisted incorrectly.

Input

JavaScript
function render({ text }) {
  return () => (<Component text={text} />);
}

Output

JavaScript
function render(_ref) {
  let text = _ref.text;
  var _ref2 = <Component text={text} />;
  return () => _ref2;
}

🌏 Committers: 10​

Check out Github for the whole changelog!