parseInt

语法

描述

The parseInt function parses its first argument, a string, and attempts to return an integer of the specified radix (base). For example, a radix of 10 indicates to convert to a decimal number, 8 octal, 16 hexadecimal, and so on. For radixes above 10, the letters of the alphabet indicate numerals greater than 9. For example, for hexadecimal numbers (base 16), A through F are used.

If parseInt encounters a character that is not a numeral in the specified radix, it ignores it and all succeeding characters and returns the integer value parsed up to that point. parseInt truncates numbers to integer values.

If the radix is not specified or is specified as 0, JavaScript assumes the following:

• If the input string begins with "0x", the radix is 16 (hexadecimal).
• If the input string begins with "0", the radix is eight (octal).
• If the input string begins with any other value, the radix is 10 (decimal).

For arithmetic purposes, the "NaN" value is not a number in any radix. You can call the isNaN function to determine if the result of parseInt is "NaN". If "NaN" is passed on to arithmetic operations, the operation results will also be "NaN".

示例

parseInt("F", 16)
parseInt("17", 8)
parseInt("15", 10)
parseInt(15.99, 10)
parseInt("FXX123", 16)
parseInt("1111", 2)
parseInt("15*3", 10) The following示例 all return "NaN":

parseInt("Hello", 8)
parseInt("0x7", 10)
parseInt("FFF", 10) Even though the radix is specified differently, the following示例 all return 17 because the input string begins with "0x".

parseInt("0x11", 16)
parseInt("0x11", 0)
parseInt("0x11")

参看