Native deep cloning
It's called "structured cloning", works experimentally in Node 11 and later, and hopefully will land in browsers. See this answer for more details.
Fast cloning with data loss - JSON.parse/stringify
If you do not use Date
s, functions, undefined
, Infinity
, RegExps, Maps, Sets, Blobs, FileLists, ImageDatas, sparse Arrays, Typed Arrays or other complex types within your object, a very simple one liner to deep clone an object is:
JSON.parse(JSON.stringify(object))
const a = {
string: 'string',
number: 123,
bool: false,
nul: null,
date: new Date(), // stringified
undef: undefined, // lost
inf: Infinity, // forced to 'null'
re: /.*/, // lost
}
console.log(a);
console.log(typeof a.date); // Date object
const clone = JSON.parse(JSON.stringify(a));
console.log(clone);
console.log(typeof clone.date); // result of .toISOString()
See Corban's answer for benchmarks.
Reliable cloning using a library
Since cloning objects is not trivial (complex types, circular references, function etc.), most major libraries provide function to clone objects. Don't reinvent the wheel - if you're already using a library, check if it has an object cloning function. For example,
- lodash -
cloneDeep
; can be imported separately via the lodash.clonedeep module and is probably your best choice if you're not already using a library that provides a deep cloning function
- AngularJS -
angular.copy
- jQuery -
jQuery.extend(true, { }, oldObject)
; .clone()
only clones DOM elements
- just library -
just-clone
; Part of a library of zero-dependency npm modules that do just do one thing.
Guilt-free utilities for every occasion.
ES6 (shallow copy)
For completeness, note that ES6 offers two shallow copy mechanisms: Object.assign()
and the spread syntax.
which copies values of all enumerable own properties from one object to another. For example:
var A1 = {a: "2"};
var A2 = Object.assign({}, A1);
var A3 = {...A1}; // Spread Syntax
Converts Object
to boolean
. If it was falsey (e.g. 0
, null
, undefined
, etc.), it will be false
, otherwise, true
.
!oObject // inverted boolean
!!oObject // non inverted boolean so true boolean representation
So !!
is not an operator, it's just the !
operator twice.
Real World Example "Test IE version":
const isIE8 = !! navigator.userAgent.match(/MSIE 8.0/);
console.log(isIE8); // returns true or false
If you ⇒
console.log(navigator.userAgent.match(/MSIE 8.0/));
// returns either an Array or null
But if you ⇒
console.log(!!navigator.userAgent.match(/MSIE 8.0/));
// returns either true or false
Best Answer
This is a new feature of NPM called 'scoped packages', which effectively allow NPM packages to be namespaced. Every user and organization on NPM has their own scope, and they are the only people who can add packages to it.
This is useful for several reasons:
@angular
, you know it was published by the Angular core team.http
is already taken in the main repository, but Angular is able to have@angular/http
as well.The reason that scoped packages don't show up in public search is because a lot of them are private packages created by organizations using NPM's paid services, and they're not comfortable opening the search up until they can be totally certain they're not going to make anything public that shouldn't be public - from a legal perspective, this is pretty understandable.
For more information, see the NPM docs and the Angular docs.
EDIT: It appears that public scoped packages now show up properly in search!