Question

Suppose that you want to check what input string a user has entered in a form field. Which one would be the fastest way to check this input against a list of possible values?

The following examples use jQuery.

First method: using ||

if (input == "firstValue" || input == "secondValue" || ... ) {
    ...
}

Second method: using inArray()

if ($.inArray(input, array) >= 0) {
    ...
}

Are there any significant differences between these two methods?

Answer 1

You don’t want the fastest but the most readable way. And that’s in_array() (JavaScript: array.indexOf(value) >= 0) for more than 2 or 3 values.

The performance difference is negligible – while a function call and array creation certainly has some overhead, it doesn’t matter compared to expensive operations such a file access, database access, network access, etc.. So in the end nobody will notice the difference.

Here’s a short benchmark, each with 1 million iterations:

5.4829950332642 - in_array, the array is recreated everytime
2.9785749912262 - in_array, the array is created only once
0.64996600151062 - isset(), the array way created only once and then the values were turned to keys using array_flip()
2.0508298873901 - ||

So, the fastest, yet still very readable way is this. Unless you create $arr only once and use it many times, there is no need for this and you can simply stay with in_array().

$arr = array_flip(array('your', 'list', 'of', 'values'));
if(isset($arr[$value])) ...

---

In case you did ask for JavaScript (in this case get rid of those $ prefixes!), the best solution is using Array.indexOf():

['a', 'b', 'c'].indexOf(value) >= 0

However, not all browsers already support Array.indexOf(), so you might want to use e.g. the function from Underscore.js:

_.contains(['a', 'b', 'c'], value)

jQuery also has a function for this:

$.inArray(value, ['a', 'b', 'c'])

The fastest way would be with an object and the in operator, but the object definition is less readable than the array definition:

value in {'a':0, 'b':0, 'c':0}

Here’s a JSPerf benchmark for the various solutions: http://jsperf.com/inarray-vs-or – but again, the rather big performance difference is negligible in most cases since you are not going to execute the code millions of times in a loop.