What is parseint..,and where to use...

Answer 1

> parseInt(10)=>10
> parseInt(10, 16)=>16
> parseInt(10, 2)=>2
> parseInt(10, 3)=>3
> parseInt("10")=>10
> parseInt("10", 16)=>16
> parseInt("0x10")=>16
> parseInt("0x10", 10)=>0
> parseInt("0hello10")=>0
> parseInt("10hello10")=>10
> parseInt("0x10hello10")=>16
> parseInt("hello")=>NaN
> parseInt("21", 2)=>NaN
> parseInt("BAD")=>NaN
> parseInt("BAD", 16)=>2989
> parseInt({a: 10})=>NaN
> parseInt(Math.max)=>NaN

So, briefly, parseInt tries to give you a number out of arbitrary input. If it finds anything meaningful, it returns it. If it doesn't - you get NaN. You can optionally provide second argument representing the radix to be used for parsing. If you don't, parseInt tries to guess it from the prefixes.