Hudson Kim
Hudson Kim
2,965 Points

What is the parse int function and what does it do?

SO what exactly does the parse int do? I looked it up but all the explanation seem to be confusing me even more. Please help me understand. Thanks.

1 Answer

Antti Lylander
Antti Lylander
9,647 Points

It converts a string to a number. It only searches the number in the beginning of the string though. If the first character is not a number, NaN is returned.

You can try different values in the console.

parseInt('15 miles') //returs 15
parseInt('about 15 miles') //returns NaN

input = prompt('give an integer') //try giving it an integer, it will return "3" if you type in 3.
typeof input //try then this in console. it will return "string"

integer = parseInt(input) //this will return 3 (no double quotes, meaning that it is a number, not a string anymore)
typeof integer //this returns "number" so now you know that your value is stored as a number and you are safe doing some math with it. Many math methods do the conversion automatically, but it is not a good practice to count on it.

I guess you have been using it with prompt(). The reason for that is the fact that prompt always returns a string value even if you type a number in the prompt. Hope this clears it a bit. Trying stuff in console always helps me.