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javascriptparseint

ParseInt() strange octal behavior

I have to convert some input data to integer. I found parseInt() function.
Everything is good if the input is string:

console.log(parseInt("123")) //123

Even if the string starts with 0:

console.log(parseInt("0123")) //123

But if a number starts with 0, it will give 83!

    console.log(parseInt(0123)) //83 instead of 123

I heard about that's because octal behavior (Javascript parseInt() with leading zeros), so I gave a radix parameter to it:

    console.log(parseInt(0123,10)) //83!!!

Still 83!!!

And then, the strangest of all:
I thinked: octal 123 must give 123 in octal! But it gave NaN:

console.log(parseInt(0123, 8)) //NaN

Why this strange behavior?! And how can I fix it?

Thanks!!!

Solution

  • In this code, you can defined a number (rather than a string) in octal format, then passed it to parseInt. Then parseInt casts that number to a string ("83"), and parses it again.

    If you pass a string to parseInt you will get the expected result:

    console.log(parseInt('0123'))