二分查找算法-Node.js实现

/**
 * 
 * @param {*} arr 有序数组
 * @param {*} firstNumIndex 第一个值的索引
 * @param {*} lastNumIndex 最后一个值的索引
 * @param {*} target 想要查找的值
 */

function binarySearch(arr, target) {
    var firstNumIndex = 0,
        lastNumIndex = arr.length - 1;

    while (firstNumIndex <= lastNumIndex) {
        var mid = Math.floor((lastNumIndex + firstNumIndex) / 2);
        //var mid = parseInt((lastNumIndex + firstNumIndex) / 2);
        if (target == arr[mid]) {
            console.log(mid); // 0
            return;
        }
        if (target > arr[mid]) {
            firstNumIndex = mid + 1;
        } else if (target < arr[mid]) {
            lastNumIndex = mid - 1;
        }
    }
}

var arr = [-1, 3, 5, 7, 89, 101]
var num = -1;

binarySearch(arr, num)