JavaScript/jQuery equivalent of LINQ Any()

Question

Is there an equivalent of IEnumerable.Any(Predicate<T>) in JavaScript or jQuery?

I am validating a list of items, and want to break early if error is detected. I could do it using $.each, but I need to use an external flag to see if the item was actually found:

var found = false;
$.each(array, function(i) {
    if (notValid(array[i])) {
        found = true;
    }
    return !found;
});

What would be a better way? I don't like using plain for with JavaScript arrays because it iterates over all of its members, not just values.

score 125 · Answer 1 · answered May 02 '14 at 01:58

125

These days you could actually use Array.prototype.some (specced in ES5) to get the same effect:

array.some(function(item) {
    return notValid(item);
});

answered May 02 '14 at 01:58

Sean Vieira

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quick summary: `some()` executes the callback function once for each element present in the array until it finds one where callback returns a true value. If such an element is found, `some()` immediately returns true. Otherwise, `some()` returns false. – Simon_Weaver May 14 '15 at 09:15
1

This is the right answer if you can use it. It is an equivalent function to Linq.Any() – Ed Bishop Mar 01 '16 at 12:23
If you need IE8 compatibility, then this is not an option. – Akira Yamamoto Jul 20 '17 at 07:02
1

Update: In ES6 / ECMAScript 2015, you can do `myArray.some(c=>c)` to mimic exactly what LINQ does with .Any(). Noting that in LINQ the .Any() method doesn't require a delegate, whereas .some() does. Attempting to call .some() without a delegate will result in an error as the delegate will be undefined. – Hardrada Sep 11 '20 at 21:18

score 19 · Answer 2 · edited May 02 '14 at 01:48

19

You could use variant of jQuery is function which accepts a predicate:

$(array).is(function(index) {
    return notValid(this);
});

edited May 02 '14 at 01:48

Simon_Weaver

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answered May 10 '11 at 13:19

Xion

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I think you should avoid using `this` inside the `is` function when used for an `array`. Because you won't get the original type (so comparission using "===" will fail). I'd use `array[i]` instead. See this: http://jsfiddle.net/BYjcu/3/ – Mariano Desanze Jul 04 '13 at 23:18
This is interesting (my [fiddle to confirm](https://jsfiddle.net/mlhDevelopment/LmrfpvLq/)) but my gut reaction is to avoid this approach since it is operating a selection function `$.fn.is` over a collection that is not a jQuery selection (a native array). If there was a utility function like `$.is` I'd feel safer, but this appears to be an undocumented "feature" – mlhDev Dec 30 '16 at 14:42
AFAIK jQuery selections _are_ native arrays (or at least they use `Array.prototype`), and there is probably enough code in the wild relying on it that it can never change. This saying, this answer is almost six years old. These days you should be using native ES5 approach shown nearby, or something like LoDash/Underscore/etc. that has API specifically for dealing with native JS arrays. – Xion Jan 01 '17 at 18:21
You're right, I did not notice the date on this answer. Sorry about that (and now I can't undo my downvote!) – mlhDev Jan 03 '17 at 18:05

score 4 · Answer 3 · answered Jul 21 '11 at 17:33

4

Xion's answer is correct. To expand upon his answer:

jQuery's .is(function) has the same behavior as .NET's IEnumerable.Any(Predicate<T>).

From http://docs.jquery.com/is:

Checks the current selection against an expression and returns true, if at least one element of the selection fits the given expression.

answered Jul 21 '11 at 17:33

Scott Rippey

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Was this supposed to be a comment or edit on their answer? It seems to only agree with that answer, adding a bit of context? – Kissaki Dec 20 '21 at 13:47

score 3 · Answer 4 · answered Sep 05 '16 at 14:55

3

You might use array.filter (IE 9+ see link below for more detail)

[].filter(function(){ return true|false ;}).length > 0;

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter

answered Sep 05 '16 at 14:55

Anthony Johnston

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score 3 · Answer 5 · answered May 10 '11 at 13:17

3

You should use an ordinary for loop (not for ... in), which will only loop through array elements.

answered May 10 '11 at 13:17

SLaks

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*could (I think you meant to say) – Simon_Weaver Jun 30 '13 at 00:43
@Simon_Weaver: No; he _should not_ use `for in` to iterate arrays. – SLaks Jun 30 '13 at 02:18
4

@SLaks, you have misunderstood Simon_Weaver's comment! "You *could* use an ordinary for loop." Rather than "You *should*..." – Chris Haines Mar 19 '14 at 16:46
Well it definitely says *should* right there in the text. You can’t say they were misunderstood when it is literally written there. – Kissaki Dec 20 '21 at 13:48

Erick Petrucelli · Answer 6 · 2021-07-20T20:54:01.533

I suggest you to use the $.grep() method. It's very close to IEnumerable.Any(Predicate<T>):

$.grep(array, function(n, i) {
  return (n == 5);
});

Here a working sample to you: http://jsfiddle.net/ErickPetru/BYjcu/.

2021 Update

This answer was posted more than 10 years ago, so it's important to highlight that:

When it was published, it was a solution that made total sense, since there was nothing native to JavaScript to solve this problem with a single function call at that time;
The original question has the jQuery tag, so a jQuery-based answer is not only expected, it's a must. Down voting because of that doesn't makes sense at all.
JavaScript world evolved a lot since then, so if you aren't stuck with jQuery, please use a more updated solution! This one is here for historical purposes, and to be kept as reference for old needs that maybe someone still find useful when working with legacy code.

@Groo: I didn't said that `Any(Predicate)` is the most closest method to `grep()`, only is very near. I agree that `FindAll(Predicate)` is much more close to it. But both are near. — Erick Petrucelli, May 11 '11 at 12:52

score 1 · Answer 7 · answered May 10 '11 at 14:47

1

I would suggest that you try the JavaScript for in loop. However, be aware that the syntax is quite different than what you get with a .net IEnumerable. Here is a small illustrative code sample.

var names = ['Alice','Bob','Charlie','David'];
for (x in names)
{
    var name = names[x];
    alert('Hello, ' + name);
}

var cards = { HoleCard: 'Ace of Spades', VisibleCard='Five of Hearts' };
for (x in cards)
{
    var position = x;
    var card = card[x];
    alert('I have a card: ' + position + ': ' + card);
}

answered May 10 '11 at 14:47

Vivian River

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I believe OP wanted to say with *plain `for` (...) iterates over all of its members* that use of `for in` can sometimes [yield unexpected results](http://stackoverflow.com/questions/500504/javascript-for-in-with-arrays/500531#500531) (if `Array.prototype` is extended, or if you implicitly resize arrays). – vgru May 11 '11 at 09:20

score 1 · Answer 8 · answered Aug 23 '21 at 16:16

Necromancing.
If you cannot use array.some, you can create your own function in TypeScript:

interface selectorCallback_t<TSource> 
{
    (item: TSource): boolean;
}


function Any<TSource>(source: TSource[], predicate: selectorCallback_t<TSource> )
{
    if (source == null)
        throw new Error("ArgumentNullException: source");
    if (predicate == null)
        throw new Error("ArgumentNullException: predicate");

    for (let i = 0; i < source.length; ++i)
    {
        if (predicate(source[i]))
            return true;
    }

    return false;
} // End Function Any

Which transpiles down to

function Any(source, predicate) 
 {
    if (source == null)
        throw new Error("ArgumentNullException: source");
    if (predicate == null)
        throw new Error("ArgumentNullException: predicate");
    for (var i = 0; i < source.length; ++i) 
    {
        if (predicate(source[i]))
            return true;
    }
    return false;
}

Usage:

var names = ['Alice','Bob','Charlie','David'];
Any(names, x => x === 'Alice');

JavaScript/jQuery equivalent of LINQ Any()

8 Answers8

2021 Update