Table of contents
- 1. Summary
- 2. Syntax
- 3. Parameters
- 4. Description
- 5. Examples
- 6. See also
Summary
Core Function
Parses a string argument and returns an integer of the specified radix or base.
Syntax
var intValue = parseInt(string[, radix]);
Parameters
string- A string that represents the value you want to parse.
radix- An integer that represents the radix of the above mentioned string. While this parameter is optional, always specify it to eliminate reader confusion and to guarantee predictable behavior. Different implementations produce different results when a radix is not specified.
Description
parseInt is a top-level function and is not associated with any object.
Function parseInt converts its first argument to a string, parses it, and returns an integer or NaN. If not NaN, the returned value will be the decimal integer representation of the first argument taken as a number in the specified radix (base). For example, a radix of 10 indicates to convert from a decimal number, 8 octal, 16 hexadecimal, and so on. For radices 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. Leading and trailing spaces are allowed.
If radix is undefined or 0, JavaScript assumes the following:
- If the input
stringbegins with "0x" or "0X", radix is 16 (hexadecimal). - If the input
stringbegins with "0", radix is eight (octal). This feature is non-standard, and some implementations deliberately do not support it (instead using the radix 10). For this reason always specify a radix when usingparseInt. - If the input
stringbegins with any other value, the radix is 10 (decimal).
If the first character cannot be converted to a number, parseInt returns NaN.
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.
To convert number to its string literal in a particular radix use intValue.toString(radix).
Examples
Example: Using parseInt
The following examples all return 15:
parseInt(" 0xF", 16);
parseInt(" F", 16);
parseInt("17", 8);
parseInt(021, 8);
parseInt("015", 10);
parseInt(15.99, 10);
parseInt("FXX123", 16);
parseInt("1111", 2);
parseInt("15*3", 10);
parseInt("15e2", 10);
parseInt("15px", 10);
parseInt("12", 13);
The following examples all return NaN:
parseInt("Hello", 8); // Not a number at all
parseInt("546", 2); // Digits are not valid for binary representations
The following examples all return -15:
parseInt("-F", 16);
parseInt("-0F", 16);
parseInt("-0XF", 16);
parseInt(-10, 16);
parseInt(-15.1, 10)
parseInt(" -17", 8);
parseInt(" -15", 10);
parseInt("-1111", 2);
parseInt("-15e1", 10);
parseInt("-12", 13);
The following example returns 224:
parseInt("0e0", 16);
Although it is optional, most implementations interpret a numeric string beginning with a leading '0' as octal. The following may have an octal result.
parseInt("0e0"); // 0
parseInt("08"); // 0, '8' is not an octal digit.
