SOURCE

// 二分查找
const arr = [1, 3, 4, 6, 7, 9]

const search = (arr, target, start, end) => {
    if (start === undefined) {
        start = 0
    }
    if (end === undefined) {
        end = arr.length - 1
    }
    let midIndex = Math.floor((start + end) / 2)
    if (target === arr[midIndex]) {
        return midIndex
    }
    if (target > arr[midIndex]) {
        return search(arr, target, midIndex + 1, end)
    }
    if(target < arr[midIndex]){
        return search(arr, target, start, midIndex - 1)
    }
}

console.log(search(arr, 3))