CODEWITHSUNDEEP
javascriptangulartypescriptdestructuring
Jagadeesh Govindaraj
Jagadeesh Govindaraj

Reputation: 8305

Typescript swap array Items

how to swap two elements using typescript 

elements:elements[] =[];
elements.push(item1);
elements.push(item2);
elements.push(item3);
elements.push(item4);


elements[0] is item1 
elements[3] is item4

How can i interchange these items in typescript. i know Javascript way, like this:

*javascript example using temp variable *

var tmp = elements[0];
elements[0] = elements[3];
elements[3] = tmp;

but there is any api doing same thing in typescript like array.swap()

Upvotes: 9

Views: 28514

Answers (5)

vykaash
vykaash

Reputation: 96

This question is old but if you're like me you may have come across this post checking for built in swap behavior.

The accepted answer uses de-structuring, and it's fine but it is slower than using a temp to swap elements. If performance is a concern use the temp method as OP has described.

A benchmark

The result is de-structuring is an order of magnitude slower than the temp method.

enter image description here

Upvotes: 1

rmcsharry
rmcsharry

Reputation: 5562

You can do this in one line in Javascript (and therefore Typescript, although in Typescript you can do array destructure as shown in another answer).

For primitive types (eg. integers, strings) you can do this to swap simple values a and b around (credit here):

a = [b, b=a][0];

So if you had an array with 3 elements, like so: a=['me','you','us']

You can swap 'me' and 'you' like this:

a = [a[1],a[1]=a[0],a[2]]

So taking the OP's 4 element array, to swap the first (0th) and last (3rd) elements, you would do:

elements = [elements[3],elements[1],elements[2],elements[3]=elements[0]]

However, that is not easy to understand code, so I don't recommend it. Using a tmp variable is more straightforward. Also, it's not very performant or maintainable since you have to specify every element of the original array.

Upvotes: 1

Kapein
Kapein

Reputation: 175

swapArray(Array:any,Swap1:number,Swap2:number) : any
{
    var temp = Array[Swap1];
    Array[Swap1] = Array[Swap2]
    Array[Swap2] = temp
    return Array;
}

Upvotes: 4

Nitzan Tomer
Nitzan Tomer

Reputation: 164217

There's no builtin functionality for it, but you can easily add it:

interface Array<T> {
    swap(a: number, b: number): void;
}

Array.prototype.swap = function (a: number, b: number) {
    if (a < 0 || a >= this.length || b < 0 || b >= this.length) {
        return
    }

    const temp = this[a];
    this[a] = this[b];
    this[b] = temp;
}

(code in playground)

If you are using modules then you'll need to do this to augment the Array interface:

declare global {
    interface Array<T> {
        swap(a: number, b: number): void;
    }
}

Upvotes: 4

Nina Scholz
Nina Scholz

Reputation: 386654

Why not use destructuring and an array.

[elements[0], elements[3]] = [elements[3], elements[0]];

Upvotes: 62

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