leetcode-8 字符串转换整数 (atoi)

/**
 * @param {string} s
 * @return {number}
 */
var myAtoi = function (s) {
  // 忽略空格
  let i = 0;
  while (s[i] === " ") {
    i++;
  }
  s = s.slice(i);
  // 正负号
  let negativeFlag = 1;
  while (s[0] === "-" || s[0] === "+") {
    if (s[0] === "-") {
      negativeFlag *= -1;
    }
    s = s.slice(1);
  }
  // 计算
  let result = 0;
  for (let i = 0; i < s.length; i++) {
    if (/[0-9]/.test(s[i])) {
      result = result * 10 + parseInt(s[i]);
    } else {
      break;
    }
  }
  result *= negativeFlag;
  if (result < -Math.pow(2, 31)) {
    return -Math.pow(2, 31);
  }
  if (result > Math.pow(2, 31) - 1) {
    return Math.pow(2, 31) - 1;
  }
  return result;
};
console.log(myAtoi("42"));
console.log(myAtoi("-42"));