算法，折半查找--javascript版

var arr = [1,2,4,6,9,10,12,15];
function searchKey(arr, key) {
	var mid = parseInt(arr.length/2);
	var midValue = arr[mid]; 
	if(key === midValue){
		return midValue;
	}else if(key > midValue){
		return searchKey(arr.slice(mid+1), key);
	}else if(key < midValue){
		return searchKey(arr.slice(0, mid), key);
	}else{
		return false;
	}
}
function print(arr, key) {
	var res = searchKey(arr, key);
	if(typeof res === "number") {
		console.log("找到了");
	}else{
		console.log("呜呜，没找到！");
	}
}
print(arr, 1);

　　缺点是不能打印出准确位置；

　　下面这种参考大神的写法；

var arr = [1,2,4,6,9,10,12,15];
function searchKey(arr, key) {
    var high = arr.length - 1;
    var low = 0,middle,midValue;
    while(low <= high) {
        middle = parseInt( (low + high) / 2 );
        midValue = arr[middle];
        if(midValue === key) {
            return middle;
        }else if(midValue > key){
            high = middle - 1;
        }else if(midValue < key){
            low = middle + 1;
        }else{
            return "错误的参数";
        }
    }
    return false;
    
}
function print(arr, key) {
    var res = searchKey(arr, key);
    if(typeof res === "number") {
        console.log("找到了,位置是" + res);
    }else{
        console.log("呜呜，没找到！");
    }
}
print(arr, 1);