myGlobal.parseInt( string, [ radix ] ) in ECMAScript 262

Attempt to convert a string into an integer number, using the specified base.


string String The string to convert to a num
radix Number [optional] The base for the conversion.
Return Type


In most cases, var strAsNum = myStr*1; or var strAsnum = +myStr; are more appropriate than using var strAsNum = parseInt(myStr,10). (And they're faster, too.)

Although radix is not required, it should not be omitted. This is because when omitted, it takes on one of three values, depending on the string:

Given the above, parseInt('11') returns 11, while parseInt('011') returns 9. Because of this, you should always specify your desired base (usually 10) when parsing input from a user.

Unlike an implicit (and faster) conversion to a number by multiplying a value by 1 (e.g. var x='17'; x=x*1;), parseInt reads up to the first character which does not fit the specified radix, and ignores the rest. See the following example for the implications of this:

var userInput1 = "$1,000";
var userInput2 = "1,000";
var userInput3 = "     15zzzzz";
var userInput4 = "1.34";

var val1,val2,val3,val4;

val1 = userInput1*1;            //NaN -- bad characters found
val1 = parseInt(userInput1,10); //NaN -- no valid characters found before invalid ones

val2 = userInput2*1;            //NaN -- bad characters found
val2 = parseInt(userInput2,10); //1 -- the user meant "1000", but the script turned it into just "1", stopping at the comma

val3 = userInput3*1;            //NaN -- bad characters found
val3 = parseInt(userInput3,10); //15 -- leading spaces are ignored, and the conversion stops at the first 'z'

val4 = userInput4*1;            //1.34
val4 = parseInt(userInput4,10); //1 -- the conversion stopped when it hit the decimal. See parseFloat

Despite the above, this function has its uses in user interaction, and is the only way to convert a string into a number using a base other than 10.

var x = parseInt('01011',2); //11
var y = parseInt('ff',16);   //255