Destructuring in Node.JS

This recent video claims that EMCAScript 6 destructuring is already partially implemented in Node.JS. I have tried various examples (using v0.10.12 and the --harmony flag), such as

var [a, b] = [1, 2];

and

var {a: a, b: b} = {a: 1, b: 2};

to no avail. This ticket seems to suggest that destructuring is not yet supported in V8.

Is destructuring really partially implemented in Node.JS? What are snippets of code I can play with?

44481 次浏览

Update for node v6 and newer: Node v6 supports destructuring assignment without anything special needed:

var [a, b] = [1, 2];

For older versions of node: You can get the list of supported harmony features by typing:

node --v8-options | grep harmony

node 5.x will give you:

--es_staging (enable all completed harmony features)
--harmony (enable all completed harmony features)
--harmony_shipping (enable all shipped harmony fetaures)
--harmony_modules (enable "harmony modules" (in progress))
--harmony_regexps (enable "harmony regular expression extensions" (in progress))
--harmony_proxies (enable "harmony proxies" (in progress))
--harmony_sloppy_function (enable "harmony sloppy function block scoping" (in progress))
--harmony_sloppy_let (enable "harmony let in sloppy mode" (in progress))
--harmony_unicode_regexps (enable "harmony unicode regexps" (in progress))
--harmony_reflect (enable "harmony Reflect API" (in progress))
--harmony_destructuring (enable "harmony destructuring" (in progress))
--harmony_default_parameters (enable "harmony default parameters" (in progress))
--harmony_sharedarraybuffer (enable "harmony sharedarraybuffer" (in progress))
--harmony_atomics (enable "harmony atomics" (in progress))
--harmony_simd (enable "harmony simd" (in progress))
--harmony_array_includes (enable "harmony Array.prototype.includes")
--harmony_tostring (enable "harmony toString")
--harmony_concat_spreadable (enable "harmony isConcatSpreadable")
--harmony_rest_parameters (enable "harmony rest parameters")
--harmony_sloppy (enable "harmony features in sloppy mode")
--harmony_arrow_functions (enable "harmony arrow functions")
--harmony_new_target (enable "harmony new.target")
--harmony_object_observe (enable "harmony Object.observe")
--harmony_spreadcalls (enable "harmony spread-calls")
--harmony_spread_arrays (enable "harmony spread in array literals")
--harmony_object (enable "harmony Object methods")

The flag you need, --harmony_destructuring, was added in Node 4.1. Currently, you'll need to pass the --harmony_destructuring flag to enable the feature:

$ node --harmony_destructuring
> var {foo} = {foo: 'bar'};
undefined
> foo
'bar'

The ES6 compatibility table shows that destructuring isn't supported in either Chrome 45, or Node v4.

The lately released node.js v6 is using V8 version 5.0 which is supporting 93% of ES2015 language features (even 96% in v6.1).

Destructuring assignments can now be considered stable and can be used without any flags.