Why are leading zeroes used to represent octal num

问题:

I've always wondered why leading zeroes (0) are used to represent octal numbers, instead of — for example — 0o. The use of 0o would be just as helpful, but would not cause as many problems as leading 0es (e.g. parseInt('08'); in JavaScript). What are the reason(s) behind this design choice?

回答1:

All modern languages import this convention from C, which imported it from B, which imported it from BCPL.

Except BCPL used #1234 for octal and #x1234 for hexadecimal. B has departed from this convention because # was an unary operator in B (integer to floating point conversion), so #1234 could not be used, and # as a base indicator was replaced with 0.

The designers of B tried to make the syntax very compact. I guess this is the reason they did not use a two-character prefix.

回答2:

"0b" is often used for binary rather than for octal. The leading "0" is, I suspect for "O -ctal".

If you know you are going to be parsing octal then use parseInt('08', 10); to make it treat the number as base ten.