How to replace item in array?

javascript arrays

2022-08-29 23:06:41

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 with , how would we do this?34521010

答案 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 comparison:~-1

var index = items.indexOf(3452);

if (~index) {
    items[index] = 1010;
}

Sometimes I even like to write a 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:contains

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
}

答案 2

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