How to replace item in array?

Question

Each item of this array is some number:

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

How to replace some item with a new one?

For example, we want to replace 3452 with 1010, how would we do this?

Answer 1

var index = items.indexOf(3452);  if (index !== -1) {     items[index] = 1010; } 

Also it is recommend you not use the constructor method to initialize your arrays. Instead, use the literal syntax:

var items = [523, 3452, 334, 31, 5346]; 

You can also use the ~ operator if you are into terse JavaScript and want to shorten the -1 comparison:

var index = items.indexOf(3452);  if (~index) {     items[index] = 1010; } 

Sometimes I even like to write a contains function to abstract this check and make it easier to understand what's going on. What's awesome is this works on arrays and strings both:

var contains = function (haystack, needle) {     return !!~haystack.indexOf(needle); };  // can be used like so now: if (contains(items, 3452)) {     // do something else... } 

Starting with ES6/ES2015 for strings, and proposed for ES2016 for arrays, you can more easily determine if a source contains another value:

if (haystack.includes(needle)) {     // do your thing }