根据while的判断条件,left左边的值一直小于target,右边的值一直大于等于target,当跳出while时,left最终等于right-1,此时插入的值就在left
var searchInsert = function(nums, target) {
let left = 0;
let right = nums.length-1;
while(left<=right){
const mid = Math.floor((nums[right]-nums[right]))+right;
const cur = nums[mid];
if(cur === target) return mid;
if(cur < target){
left ++;
}else{
right--;
}
}
return left
};