(Deep) copying an array using jQuery

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What is the most efficient way to clone a JavaScript object?

I need to copy an (ordered, not associative) array of objects. I'm using jQuery. I initially tried 

jquery.extend({}, myArray)

but, naturally, this gives me back an object, where I need an array (really love jquery.extend, by the way).

So, what's the best way to copy an array?

jquery javascript
8 Answers

Since Array.slice() does not do deep copying, it is not suitable for multidimensional arrays:

var a =[[1], [2], [3]];
var b = a.slice();

b.shift().shift();
// a is now [[], [2], [3]]

Note that although I've used shift().shift() above, the point is just that b[0][0] contains a pointer to a[0][0] rather than a value.

Likewise delete(b[0][0]) also causes a[0][0] to be deleted and b[0][0]=99 also changes the value of a[0][0] to 99.

jQuery's extend method does perform a deep copy when a true value is passed as the initial argument:

var a =[[1], [2], [3]];
var b = $.extend(true, [], a);

b.shift().shift();
// a is still [[1], [2], [3]]
user_554780

$.extend(true, [], [['a', ['c']], 'b'])

That should do it for you.

user_502140

I realize you're looking for a "deep" copy of an array, but if you just have a single level array you can use this:

Copying a native JS Array is easy. Use the Array.slice() method which creates a copy of part/all of the array.

var foo = ['a','b','c','d','e'];
var bar = foo.slice();

now foo and bar are 5 member arrays of 'a','b','c','d','e'

of course bar is a copy, not a reference... so if you did this next...

bar.push('f');
alert('foo:' + foo.join(', '));
alert('bar:' + bar.join(', '));

you would now get:

foo:a, b, c, d, e
bar:a, b, c, d, e, f
user_61440

Everything in JavaScript is pass by reference, so if you want a true deep copy of the objects in the array, the best method I can think of is to serialize the entire array to JSON and then de-serialize it back.

Admin1

how about complex types? when array contains objects... or any else

My variant:

Object.prototype.copy = function(){
    var v_newObj = {};
    for(v_i in this)
        v_newObj[v_i] = (typeof this[v_i]).contains(/^(array|object)$/) ? this[v_i].copy() : this[v_i];
    return v_newObj;
}

Array.prototype.copy = function(){
    var v_newArr = [];
    this.each(function(v_i){
        v_newArr.push((typeof v_i).contains(/^(array|object)$/) ? v_i.copy() : v_i);
    });
    return v_newArr;
}

It's not final version, just an idea.

PS: method each and contains are prototypes also.

user_12663130
Diodeus_125790
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