boopathi / babel-minify Goto Github PK

var x = 5;
if (0) var x = 0;

1st pass:

var x = 5; var x;

2nd pass:

var x = 5, x;

FunctionDeclarations inside Block Statements are let instead of var

Related discussion: https://phabricator.babeljs.io/T7475

In "use strict" environments,

{
  function a() {}
}
a()

is like

{
  let a = function a() {};
}
b();

Bug in conditionals and mangle names. Should we detect strict environments and handle them separately or assume (for this bug alone) to be use strict.

How should this be done ? What should be considered ?

{
  var x = 5;
  function a() {}
}
var x = 6;

returns

{ var b = 5; function b() {} } var a = 6;

The function name a(or something that the mangler will assign) gives this error, doesn't happen for other function names.

babel-minify options

Change from npasses to just passes.

escompress uses a similar strategy of building a minifier on top of babel transforms. It may be worth consolidating your efforts.

I posted a similar issue in escompress's issue tracker here - https://github.com/escompress/escompress/issues/10

As an example, I tried unminified React code on Chrome Canary with the browser version of the minifier and the time taken was around 19s in the worker thread.

• Calculate individual plugins perf ?

var a = function () { function b() { this } }

can be transformed to

var a = () => { function b() { this } }

Fix:
babel/babel#3557

Related:
erikdesjardins/babel-plugin-transform-dead-code-elimination#16

eg:

function foo() {
  var bar; // this can be mangled
  (1, eval)("bar = 0");
}

function-to-arrow should take keep_fnames argument and transform even more functions to arrows when keep_fnames is false.

Related - https://phabricator.babeljs.io/T7470

When a global var already exists, there is no binding, and mangler fails to check this.

var x = 1;
var y = a + 1;

and the output is

var a=1,b=a+1;

Hi, i have problem when i transpiling es6 with using babel-preset-min and plugins babel-add-module-exports

src/index.js

export default (tree, a = {}) => {
    console.log(a, tree);
    return () => {};
};

babel config

"babel": {
    "presets": [
      "es2015",
      "min"
    ],
    "plugins": [
      "add-module-exports"
    ],
    "comments": true,
    "compact": true,
    "minified": true
  }

after run $ babel src/ -d lib/ i get:

"use strict";Object.defineProperty(exports,"__esModule",{value:!0});exports.default=function(b){var c=arguments.length<=1||arguments[1]===void 0?{}:arguments[1];console.log(c,b);return function(){}};

see in end line

else run without presets min i get:

"use strict";Object.defineProperty(exports,"__esModule",{value:true});exports.default=function(tree){var a=arguments.length<=1||arguments[1]===undefined?{}:arguments[1];console.log(a,tree);return function(){}};module.exports=exports["default"];

see in end line

• constantViolations
• code deopt
• unsafe
• etc...

i have a broken build after update to v0.1.9

https://mathiasbynens.be/notes/javascript-identifiers-es6

https://github.com/mathiasbynens/regenerate

https://github.com/mathiasbynens/mothereff.in/blob/master/js-variables/tools/javascript-identifier-regex.js#L25

Plugin for global definitions