Binary_Search.js

// Function for binary search

function Binary_Search(array, search_item) 
{
    var left = 0,
        right = array.length - 1,
        middle;

    while (left <= right) 
    {
        middle = ((left + right) >> 1);

        if (array[middle] == search_item)
            return middle;

        else if (search_item < array[middle])
            right = middle - 1;

        else if (search_item > array[middle])
            left = middle + 1;
    }
    return -1;
}

var array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

var search_item = 4;

var index = Binary_Search(array, search_item);

if (index !== -1)
    console.log("found at position " + (index + 1));
else
    console.log("Not found");



/* Output

Found at position 4

*/