Binary search in multiple languages...

binary_search.js

function binarySearch (key, array) {
    var low  = 0;
    var high = (array.length - 1);

    while (low <= high) {
        var mid = floor(((low + high) / 2));
        var val = array[mid];

        if (val < key) {
            low = (mid + 1);
        } else if (val > key) {
            high = (mid - 1);
        } else {
            return mid;
        }
    }

    return null;
}

binary_search.py

def binary_search (key, array):
    low  = 0
    high = (len(array) - 1)

    while low <= high:
        mid   = int(((low + high) / 2))
        value = array[mid]

        if value < key:
            low = (mid + 1)
        elif value > key:
            high = (mid - 1)
        else:
            return mid

    return None