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up vote 24 down vote favorite
4
 
var items = Array(523,3452,334,31,...5346);

Each item of this array is some number.

How do I replace some number in with array with a new one?

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

share|improve this question
2  
Are there multiple instances of 3452 that need to be changed, or just one? –  mellamokb May 6 '11 at 19:02
3  
There will be one instance, if dark forces won't add one more. –  James May 6 '11 at 19:09

7 Answers 7

up vote 53 down vote accepted 
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...
}
share|improve this answer
1  
+1 for the !== -1 check. –  Tesserex May 6 '11 at 19:02
4  
Never knew that the ~ operator could be used this way. Thanks! –  Cheezey May 11 '13 at 19:14
up vote 15 down vote

Single-known-instance solution:

items[items.indexOf(3452)] = 1010;
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up vote 8 down vote

Use indexOf to find an element.

var i = items.indexOf(3452);
items[i] = 1010;
share|improve this answer
    
accidentally deleted my post when I thought I was confusing it with strings, then I remembered, yes, arrays do have this function too! –  Tesserex May 6 '11 at 18:57
up vote 3 down vote

Easily accomplished with a for loop.

for (var i = 0; i < items.length; i++)
    if (items[i] == 3452)
        items[i] = 1010;
share|improve this answer
2  
Easily, but not necessarily efficiently ;) –  Eli May 6 '11 at 18:59
1  
@Eli: OP wasn't clear if they were replacing one instance, or multiple instances. My solution handles multiple instances. –  mellamokb May 6 '11 at 19:02
    
Very true, I agree. –  Eli May 6 '11 at 19:03
up vote 3 down vote

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; });
share|improve this answer
3  
For anyone else reading this. Both map() and forEach() are newer additions to the Javascript spec and aren't present in some older browsers. If you want to use them, you may have to add compatibility code for older browsers: developer.mozilla.org/en/JavaScript/Reference/Global_Objects/… –  jfriend00 Jul 3 '11 at 12:12
up vote 2 down vote

you can edit any number of the list using indexes

for example : items [0]=5; items[5]=100;

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up vote 1 down vote

The easiest way is to use some libraries like underscorejs and map method.

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

_.map(items, function(num) {
  return (num == 3452) ? 1010 : num; 
});
=> [523, 1010, 334, 31, ...5346]
share|improve this answer
    
Kind of wish lodash/underscore provided an array-aware replace now..._.replace([1, 2, 3], 2, 3); –  Droogans Aug 17 '14 at 1:17

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