CODEWITHSUNDEEP
javascriptarrayscompare
Alkodurr
Alkodurr

Reputation: 38

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

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?

Upvotes: 1

Views: 1801

Answers (6)

loyola
loyola

Reputation: 4052

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!

Upvotes: 0

alexloehr
alexloehr

Reputation: 1831

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]"

Upvotes: 0

Elias Van Ootegem
Elias Van Ootegem

Reputation: 76395

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
        }
    }
}

Upvotes: 0

Clyde Lobo
Clyde Lobo

Reputation: 9174

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" );

Upvotes: 0

Bergi
Bergi

Reputation: 664277

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.

Upvotes: 1

Quentin
Quentin

Reputation: 943166

Use a for loop.

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

Upvotes: 0

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