8. 字符串转换整数 (atoi)

/**
 * @param {string} s
 * @return {number}
 */
var myAtoi = function(s) {
    const reg = /\s*([-\+]?[0-9]*).*/;

    const res = s.match(reg);

    let num
    if(res){
        num = +res[1]

        if(isNaN(num)){
            return 0
        }
    }

    let max = Math.pow(2, 31) - 1;
    let min = -max - 1;
    
    if(num > max) {
        num = max;
    } else if(num < min) {
        num = min;
    }
    return num;
};