题解 | #进制转换#

从后往前遍历即可

let len = line.length - 1;
    let res = 0;
    let bit = 0;
    while (len > 1) {
        let ditLeft = '0'.charCodeAt(0);
        let ditRight = '9'.charCodeAt(0);
        let charLeft = 'A'.charCodeAt(0);
        let charRight = 'F'.charCodeAt(0);
        let temp = line.charCodeAt(len);
        if (temp >= ditLeft && temp <= ditRight) {
            res += (temp - ditLeft) * Math.pow(16, bit);
        } else if (temp >= charLeft && temp <= charRight) {
            res += (temp - charLeft + 10) * Math.pow(16, bit)
        }
        bit += 1;
        len -= 1;
    }
    console.log(res);