Javascript Interview Question Array Binary Search without using recursion

Introduction

Implement the binarySearch function without using recursion. 

function binarySearch(array, lower, upper, target) {
   //your code here
}


var ar = [1, 10, 31, 52, 122, 291, 422, 1096];

console.log(binarySearch(ar, 0, 7, 291));

/*//from w  w  w .j av a  2  s  .  c  om
Output: ($ /usr/bin/node 005.js)
5
*/




/**
 * @function {public static} binarySearch
 *
 * Performs a binary search on a sorted `Array`.
 *
 * @param {Array} array - the `Array` to search.
 * @param {Integer} lower - the lower index to search.
 * @param {Integer} upper - the upper index to search.
 * @param {Integer} target - the element to match.
 *
 * @return the matched elements index.
 *
 * @throw exception if element is not found, or array is not ordered,
 * or indexes are not in order.
 */
function binarySearch(array, lower, upper, target) {
    var range = upper - lower;
    var center = 0;

    if (range < 0) {
        throw 'Limits are reversed.';
    }

    while (true) {
        range = upper - lower;

        if (range === 0 && array[lower] !== target) {
            throw 'Target not in array.';
        }

        if (array[lower] > array[upper]) {
            throw 'Array unordered.';
        }

        center = Math.floor(range/2) + lower;

        if (target === array[center]) {
            return center;
        }

        if (target < array[center]) {
            upper = center - 1;
        } else {
            lower = center + 1;
        }
    }
}



var ar = [1, 10, 31, 52, 122, 291, 422, 1096];

console.log(binarySearch(ar, 0, 7, 291));

/*
Output: ($ /usr/bin/node 005.js)
5
*/



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