// 二分法查找数值在数值中的区间
Array.prototype.binarySearch = function (val) { // 返回的是数组的索引值
var left = 0;
var right = this.length;
while (left <= right) {
var center = Math.floor((left + right) / 2);
if (val < this[center]) {
right = center - 1;
} else {
left = center + 1;
}
}
return right;
}
let arrY = [1, 70, 140, 210, 280, 350, 420, 490, 560];
arrY.binarySearch(y); // 返回索引值