find insert index in a sorted array

findInsertIndex.js

/**
* Implements in place binary search. O(log n)
* optional comparator can be passed
*/
function findInsertIndex(a, item, smaller) {
    var l = 0,
        len = a.length,
        r = len - 1,
        m;
    smaller = smaller || function(a, b, strict){
            return strict ? a < b : a <= b;
        };
    if (len === 0) return 0
    while (true) {
        if (smaller(item, a[l], true)) return l;
        if (smaller(a[r], item, true)) return r+1;
        if (l === r-1 && smaller(a[l], item) && smaller(item, a[r])) return r
        m = Math.floor((r + l) / 2);
        
        if (item <= a[m]) r = m
        else l = m
    }
}