How do you compare a numeric variable to each numeric element in an array in Javascript?

Question

If I have a Javascript array filled with say 10 numbers. For example (10,11,12,13,14,15,16,17,18,19) And I want to take a variable which has a value of say 20, and check to see whether any of the elements in the array are larger than 20. Because I will be comparing many arrays filled with numbers and will not know what numbers they contain.

How do you take 20 and then get Javascript to test each number in the array to find out if it is larger than 20 or not.

I know you can say something like:

var x = 20;
if (  x > myArray[0] && 
  x > myArray[1]

etc. etc. but that could mean typing out a long list of element checks. Is there a simple way like check from start index [0] to [10] or something?

Well, even if you haven't, you can use a while loop, too. (Sadly, there isn't something called goto in JavaScript...) — Alvin Wong
– Alvin Wong, Commented Oct 18, 2012 at 11:01

Bergi · Accepted Answer · 2012-10-18 11:08:11Z

1

You can use .some():

if (myArray.some(function(x) {return x > 20;}))
    // do something

It is not supported in all browsers, but you can easily shim it. Also, libraries have helper functions like this, e.g. Underscore's any.

answered Oct 18, 2012 at 11:08

Bergi

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Comments

Quentin · Accepted Answer · 2012-10-18 11:01:22Z

0

Use a for loop.

for (var i = 0; i < myArray.length; i++) {
    if (x > myArray[i]) {
         // whatever
    }
}

answered Oct 18, 2012 at 11:01

Quentin

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4 Comments

xkeshav Over a year ago

tips : write var len = myArray.length in first argument along with var iand then use len in 2nd argument in for loop

Ash Burlaczenko Over a year ago

@diEcho, thats a micro-optimization which imo sacrifices readability.

Alkodurr Over a year ago

Thanks that simple code is very helpful. I was trying to think how I could do it with a for loop, but couldn't work it out. I am pretty new to arrays though. Thanks also to everyone for all the extra replies, I will sure keep them for reference as I keep learning.

Alkodurr Over a year ago

If there is anything else I should do like tick this or that, or respond to something please tell me here as I am new around here.

Clyde Lobo · Accepted Answer · 2012-10-18 11:11:23Z

0

var x = 20;
var myArray = [10,11,12,13,14,15,16,17,18,19];
var cnt=0;

for(var i = 0; i < myArray.length; i++) {
 if(myArray[i]>x) {
   cnt++;
 }
}

alert("Found "+cnt+" values greater than "+x+" in the array" );

edited Oct 18, 2012 at 11:11

answered Oct 18, 2012 at 11:03

Clyde Lobo

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1 Comment

Elias Van Ootegem Over a year ago

Don't use for...in on arrays, that's a loop for objects

Elias Van Ootegem · Accepted Answer · 2012-10-18 11:14:34Z

0

Try this:

function getValuesFrom(array,x)
{
    x = +(x);//coerce to number
    array.sort(function(a,b)
    {
        return (a > b ? 1 : -1);
    });//sort in ascending order
    for (var i = 0;i<array.length;i++)
    {
        if (+array[i] >= x)
        {
            return array.slice(i);//return all elements >= x
        }
    }
}
var myArray = [10,11,12,13,14,15,16,17,18,19];
var larger = getValuesFrom(myArray,15);
console.log(larger);//[15,16,17,18,19]
console.log(larger.length);//5

That should do it. Note: after passing the array to this function, you might find its order is changed, to avoid this:

function getValuesFrom(array,x)
{
    x = +(x);//coerce to number
    var tmpArray = array.slice(0);//copy array
    tmpArray.sort(function(a,b)
    {
        return (a > b ? 1 : -1);
    });//sort in ascending order
    for (var i = 0;i<tmpArray.length;i++)
    {
        if (+tmpArray[i] >= x)
        {
            return tmpArray.slice(i);//return all elements >= x
        }
    }
}

edited Oct 18, 2012 at 11:14

answered Oct 18, 2012 at 11:08

Elias Van Ootegem

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1 Comment

Bergi Over a year ago

Instead of creating a new array, sorting it, and creating a subarray of the sorted one you want to use myArray.filter(function(x) {return x > 20;})?

alexloehr · Accepted Answer · 2012-10-18 11:47:18Z

0

I like using Object.prototype to extend the base functionality of JavaScript Objects. Just like the JS Frameworks prototype and MooTools do.

So introducing a new filter function to the JS Array-Object does not only solve your specific problem, but furthermore a whole class of Problems.

// extending the Array type with the new function 'filter'
// so all arrays have access to this function
// argument `fn` is a test-function which returns true or false
Array.prototype.filter = function(fn) {
    var filtered = []; // a new array for the filtered items
    for(var i = 0, len = this.length; i < len; i++) {
        var item = this[i];
        // store this item if fn returns true
        if( fn(item) ) filtered.push(item); 
    }
    return filtered;
}

// want to filter this array   
var myArr = [1,2,3,4,5,6];

// find items in myArr > 3
var myArrGt3 = myArr.filter(
    // this is the test function / must always return a bool
    function(item) {
        return item > 3;
    }
);

// testing output
document.write(JSON.stringify(myArrGt3)); // prints "[4,5,6]"

answered Oct 18, 2012 at 11:47

alexloehr

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1 Comment

Bergi Over a year ago

Neither of those libs extends Object.prototype. Also, you shouldn't overwrite Array.prototype.filter as there is already one, with even advanced options

loyola · Accepted Answer · 2015-02-17 09:42:48Z

0

You can use inArray method using jQuery.

Description: Search for a specified value within an array and return its index (or -1 if not found).

$.inArray( 5 + 5, [ 4, 5 , 7, 10 ] );  // output is 3

Example:

<script>
var arr = [ 4, "Pete", 8, "John" ];

jQuery.inArray( "John", arr ) // this returns 3(Index value of John)


</script>

Also with the help of for loop you can also loop them.

var array1=["fox","tiger","lion"];
var array2=["rat","cow","lion"];
for(i=0; i<array2.length; i++)
{
document.write(jQuery.inArray( array2[i], array1 ));
}

Output: -1 
        -1 
         2

Good day!

answered Feb 17, 2015 at 9:42

loyola

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