【笔记】二分法，有序数组中快速寻找某个元素的下标

function indexOfSorted(arr,n){
	var low = 0; 
	var high = arr.length - 1; 
	var mid = Math.ceil((low + high) / 2);
	console.log(mid);
	
	while(high > low){
		if(n == arr[low]){return low;}
		if(n == arr[high]){return high;}
		if(n == arr[mid]){return mid;} 
		if(n > arr[mid]){ low = mid; mid = Math.ceil((low + high) / 2); } 
		if(n < arr[mid]){ high = mid; mid = Math.ceil((low + high) / 2); } 
	}
}  
var sortedArr = [1,4,7,9,11,12,21,26,33]; 
console.log(indexOfSorted(sortedArr,12));