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livescript-next

Enable latest ES features for LiveScript.

What's new

• Module

import to this at top scope is compiled to module import instead, importing to other variables or at inner scope is unchanged. import name was compiled to import$(this, name), but this doesn't make sense when using modules, since this points to undefined at top scope.

import name, name1, name2: alias
import module: {name0, name1: alias1}

import name from "name";
import name1 from "name1";
import alias from "name2";

import { name0, name1 as alias1 } from "module";

export compiles to ES module export, the result works like the original when converted to common js module. The only exception is exporting named object literals, this compiles to export from instead.

export {name0, name1}
export default: name, alias: name
export external: {selected, alias1: another}

export { name0, name1 };
export { name as default, name as alias };
export { selected, another as alias1 } from "external";

• Destructing assignment and parameters

Array/object destructing is converted to its ES equivalent.

[a, b: {c: [d, e: f: g]}] = h

let a, d, g;
[a, {
  b: {
    c: [d, {
      e: {
        f: g
      }
    }]
  }
}] = h;

Function parameters, default values and splats are also converted to modern version:

function repack [a, [b=2]] ...c
  [a, ...c, b]

function repack([a, [b = 2]], ...c) {
  return [a, ...c, b];
}

• async/await

An async function is a function uses await.

--harmony flag should be passed to node 7 to enable this feature.

->
  data = await <| await fetch \https://api.github.com/gists/public .json!

(async function () {
  let data;
  return data = await (await fetch("https://api.github.com/gists/public")).json();
});

• External helpers

Helper functions are replaced with builtin functions.

a <<< b

Object.assign(a, b)

• Statement completion value

Result of statements and automatic return are converted to do expression, no need to use temporary variables.

function a b, c
  d = if b then 0
  if c
    d
  else
    1

function a(b, c) {
  let d;
  d = do {
    if (b) {
      0;
    }
  };
  return do {
    if (c) {
      d;
    } else {
      1;
    }
  };
}

• Block scope
• Arrow Functions