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JavaScript JavaScript Foundations Numbers Parsing Numbers From Strings

Jeff Lange
Jeff Lange
8,788 Points
Posted by Jeff Lange
Jeff Lange
8,788 Points

Purpose of parseInt?

The purpose of "parseInt" was defined as "getting the value of an integer out of a variable." However, can someone explain why we would need to do that? Take this example based on the code challenge I just completed:

var Q = "150";
var R = parseInt(Q);

The reason I'm confused is...couldn't we just have set variable Q to 150 (without quotes) in the first place? It basically seems like we went to extra trouble for no reason.

3 Answers

Ben Rubin
Ben Rubin
Courses Plus Student 14,658 Points

Yes, you could have set Q to 150 without the quotes. The question is just trying to demonstrate the difference between string and number variables, and show how you convert a string variable into a number variable. In a real program you'd never do what they're doing here. It's just a made up example for demonstration purposes.

Jeff Lange
Jeff Lange
8,788 Points
Jeff Lange
Jeff Lange
8,788 Points

Ah...ok that helps loads. Thanks Ben! :)

I often get confused when the code examples we type out don't actually serve a practical purpose. It's difficult for me to see ahead to what it might do, so I'm sitting there wondering "what is this doing right NOW?" haha. If you have any tips on that I'd appreciate it, but maybe it's just one of those things that I'll get better at with time. :D

Ben Rubin
PLUS
Ben Rubin
Courses Plus Student 14,658 Points
Ben Rubin
Ben Rubin
Courses Plus Student 14,658 Points

LIke you said, you'll get better with time. There are tons of ways to do anything in a program, so it's up to each programmer to find their own ways of going about things. A lot of the examples on Treehouse are just there to demonstrate a concept in isolation, so they might not be precisely how you'd do something in the real world. The more code you write, the more you'll figure out how you like to do things.

Jeff Lange
Jeff Lange
8,788 Points
Jeff Lange
Jeff Lange
8,788 Points

Yes, looks like I have Padawan Syndrome...ready to understand and do more than I'm actually ready to, haha. Thanks again, Ben, I appreciate the insight! :)

James Gill
PLUS
James Gill
Courses Plus Student 34,936 Points
James Gill
James Gill
Courses Plus Student 34,936 Points

Jeff,

In your example, you'd use parseInt because 150 is a string (and parseInt converts it to an integer). Yes, if you removed the quotes (making it an integer), you wouldn't need to use parseInt. It's as simple as that. But--it won't hurt anything.

Jeff Lange
Jeff Lange
8,788 Points
Jeff Lange
Jeff Lange
8,788 Points

I understood that part, it just didn't make sense to me why we would bother doing that if it was easier to just leave it out of quotes. See Ben's answer above--basically it was just an example not meant to actually be practical.

Thank you for stopping in to answer though, I appreciate all the help I can get! :)