Is array.slice enough to clone a multidimensional Array in JavaScript?
For example:
var array = [
[1, 2, 3],
[4, 5, 6],
[7, 8, 9]
];
var b = array.slice();
console.log(b);
I saw a secondary implementation as this from Play by Play: Lea Verou on pluralsight:
b = array.slice().map( function(row){ return row.slice(); });
The docs are pretty clear:
The
slice()method returns a shallow copy of a portion of an array into a new array object.
So the answer is no: slice by itself is not enough to clone a multidimensional array. It will only clone one dimension. You need to recursively clone each element (the way the "secondary implementation" you posted is doing) if you want a deep clone.
console.log(array[0] === b[0]);). Incidentally, in the "secondary implementation", b = array.slice().map(...) can be replaced by b = array.map(...); the map() function is returning a new array anyway, so making a shallow copy of array doesn't buy anything.From MDN:
The
slice()method returns a shallow copy of a portion of an array into a new array object.
That is, it will not clone the internal arrays / objects. Observe:
var array = [
[1, 2, 3],
[4, 5, 6],
[7, 8, 9]
];
var b = array.slice();
b[0].push(10);
console.log(array);
> [ [1, 2, 3, 10], [4, 5, 6], [7, 8, 9] ]
So if you want a deep copy of your 2D array, then you'd have to go with the map method (or something similar).
