Defaulting the radix to 8 (if the string starts with a 0) in JavaScript's parseInt function annoys me, only because I continue to forgot to pass the optional second argument as 10. I'm looking for an answer telling me why it makes sense to have it default to 8.
asked Apr 8 '11 at 20:20
Kirk OuimetKirk Ouimet
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If a number starts with 0 and contains digits between (and inclusive) 0 to 7, it is interpreted as an octal number (with base 8 instead of 10).
In parseInt however, if a string starts with a 0 it's always interpeted as an octal, and stops searching when it encounters an invalid character (e.g. the digits 8 or 9 or a character like z).
parseInt("070"); //56
parseInt("70"); //70
parseInt("070", 10); //70
parseInt("78"); //78
parseInt("078"); //7, because it stops before 8
If you need to convert a string into a number, and you're sure that it contains no invalid characters or fractional parts, you can multiply it with 1 to make a number of it:
1 * "070"; //70
I personally prefer this approach, and believe it's faster than calling functions.
answered Apr 8 '11 at 20:22
LekensteynLekensteyn
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Now, a couple of years later, parseInt() seems to work fine with numbers starting with 0. Current browsers:
parseInt("019"); // 19 on Firefox 67
parseInt("019"); // 19 on Chrome 75
parseInt("019"); // 19 on Safari 12
parseInt("019"); // 19 on IE 11
parseInt("019"); // 19 on Edge 42
But still, this "fix" must break older scripts that rely on parseInt("019") returning 1 or 0 instead of 19...