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
Modern jQuery
Use .prop()
:
$('.myCheckbox').prop('checked', true);
$('.myCheckbox').prop('checked', false);
DOM API
If you're working with just one element, you can always just access the underlying HTMLInputElement
and modify its .checked
property:
$('.myCheckbox')[0].checked = true;
$('.myCheckbox')[0].checked = false;
The benefit to using the .prop()
and .attr()
methods instead of this is that they will operate on all matched elements.
jQuery 1.5.x and below
The .prop()
method is not available, so you need to use .attr()
.
$('.myCheckbox').attr('checked', true);
$('.myCheckbox').attr('checked', false);
Note that this is the approach used by jQuery's unit tests prior to version 1.6 and is preferable to using $('.myCheckbox').removeAttr('checked');
since the latter will, if the box was initially checked, change the behaviour of a call to .reset()
on any form that contains it – a subtle but probably unwelcome behaviour change.
For more context, some incomplete discussion of the changes to the handling of the checked
attribute/property in the transition from 1.5.x to 1.6 can be found in the version 1.6 release notes and the Attributes vs. Properties section of the .prop()
documentation.
Best Answer
No. It is not possible, unless it's being done from a Firefox extension or something similar.
I'm sure you can see why this would lead to all sorts of privacy issues.