If you have a number with a leading zero, like 010 or 02, how to remove that zero?

There are various ways.

The most explicit is to use parseInt():

parseInt(number, 10)

10 is the radix, and should be always specified to avoid inconsistencies across different browsers, although some engines work fine without it.

Another way is to use the + unary operator:

+number

Those are the simplest solutions.

You can also go the regular expression route, like this:

number.replace(/^0+/, '')