JavaScript Patterns 2.8 Number Conversions with parseInt()

Strings that start with 0 are treated as octal numbers (base 8) in ECMAScript 3; however, this has changed in ES5. To avoid inconsistency and unexpected results, always specify the radix parameter:

var month = "06",

year = "09";

month = parseInt(month, 10);

year = parseInt(year, 10);

Alternative ways to convert a string to a number include:

+"08" // result is 8

Number("08") // 8

These are often faster than parseInt(), because parseInt(), as the name suggests, parses and doesn't simply convert. But if you're expecting input such as "08 hello", parseInt() will return a number, whereas the others will fail with NaN.