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javascriptfirefoxcoding-stylefirefox-addon-sdk

Why use var { VariableName } = require('') in javascript?

I have seen lot of examples in Firefox addon-sdk which uses the below style when declaring a variable. 

var { Hotkey } = require("sdk/hotkeys");

What difference it makes with var { Hotkey } than using var HotKey? Why the extra flower brackets are used?

Solution

  • This is destructuring assignment.

    var {Hotkey} = require('sdk/hotkeys');

    is equivalent to:

    var Hotkey = require('sdk/hotkeys').Hotkey;

    See also the harmony:destructuring proposal, which includes the following examples:

    // object destructuring
var { op: a, lhs: b, rhs: c } = getASTNode()

// digging deeper into an object
var { op: a, lhs: { op: b }, rhs: c } = getASTNode()