内置方法

内置方法可以直接调用。

1. parseInt
   /**

• Converts A string to an integer.
• @param s A string to convert into a number.
• @param radix A value between 2 and 36 that specifies the base of the number in numString.
• If this argument is not supplied, strings with a prefix of '0x' are considered hexadecimal.
• All other strings are considered decimal.
  */
  declare function parseInt(s: string, radix?: number): number;
  把字符串按照对应的进制转化为数字。得到的数字是10进制，radix是说字符串的进制。

var s = '110';

console.log(parseInt(s, 2));
console.log(parseInt(s, 10));
console.log(parseInt(s, 4));

6
110
20