Binary Search in Javascript

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It’s useful to write a search function in such a way that it returns a negative value indicating the insertion point for the new element if the element is not found. Also, using recursion in a binary search is excessive and unnecessary. And finally, it’s a good practice to make the search algorithm generic by supplying a comparator function as a parameter. Below is the implementation.

function binarySearch(ar, el, compare_fn) {
    var m = 0;
    var n = ar.length - 1;
    while (m <= n) {
        var k = (n + m) >> 1;
        var cmp = compare_fn(el, ar[k]);
        if (cmp > 0) {
            m = k + 1;
        } else if(cmp < 0) {
            n = k - 1;
        } else {
            return k;
        }
    }
    return -m - 1;
}

This code with comments and a unit test here.

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