The parseInt() function parses a string and returns an integer. It takes a second argument for the radix, which specifies the base of the number in the string. The radix can be an integer between 2 and 36. The function call looks like: parseInt ( string , radix ) ; And here's an example: const a = parseInt ( "11" , 2 ) ; The radix variable says that 11 is in the binary system, or base 2. This example converts the string 11 to an integer 3 . 基数是2,说的是2进制,所以二进制的11,就是十进制的3. I t converts a binary number to an integer and returns it