题解 | #获取指定字符串#

function captureThreeNumbers(str) {
    let arr = Array.from(str)
    for(let i =0;i<arr.length;i++){
        let mid = parseInt(arr[i])
        let left = parseInt(arr[i-1]) || -1
        let right = parseInt(arr[i+1]) || -1
        if(mid*2 == left+right) {
            return left +'' +mid+''+right
        }
    }
    return false
}