How to replace an item in an array with JavaScript?

Question

Each item of this array is some number.

var items = Array(523,3452,334,31, ...5346);

How do I replace some number in with array with a new on

Answer 1

The Array.indexOf() method will replace the first instance. To get every instance use Array.map():

a = a.map(function(item) { return item == 3452 ? 1010 : item; });

Of course, that creates a new array. If you want to do it in place, use Array.forEach():

a.forEach(function(item, i) { if (item == 3452) a[i] = 1010; });

Answer 2

The easiest way is this.

var items = Array(523,3452,334,31, 5346);
var replaceWhat = 3452, replaceWith = 1010;
if ( ( i = items.indexOf(replaceWhat) ) >=0 ) items.splice(i, 1, replaceWith);

console.log(items);
>>> (5) [523, 1010, 334, 31, 5346]

Answer 3

If you want a simple sugar sintax oneliner you can just:

(elements = elements.filter(element => element.id !== updatedElement.id)).push(updatedElement);

Like:

let elements = [ { id: 1, name: 'element one' }, { id: 2, name: 'element two'} ];
const updatedElement = { id: 1, name: 'updated element one' };

If you don't have id you could stringify the element like:

(elements = elements.filter(element => JSON.stringify(element) !== JSON.stringify(updatedElement))).push(updatedElement);

Answer 4

You can edit any number of the list using indexes

for example :

items[0] = 5;
items[5] = 100;

Answer 5

Replacement can be done in one line:

var items = Array(523, 3452, 334, 31, 5346);

items[items.map((e, i) => [i, e]).filter(e => e[1] == 3452)[0][0]] = 1010

console.log(items);

Or create a function to reuse:

Array.prototype.replace = function(t, v) {
    if (this.indexOf(t)!= -1)
        this[this.map((e, i) => [i, e]).filter(e => e[1] == t)[0][0]] = v;
  };

//Check
var items = Array(523, 3452, 334, 31, 5346);
items.replace(3452, 1010);
console.log(items);

Answer 6

Here's a one liner. It assumes the item will be in the array.

var items = [523, 3452, 334, 31, 5346]
var replace = (arr, oldVal, newVal) => (arr[arr.indexOf(oldVal)] = newVal, arr)
console.log(replace(items, 3452, 1010))