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I am writing a program to perform "Russian Math" (using the numberphile youtube video on it as my basis for the algorithm). It works. But, to "prove" that it works, I'm giving the user the ability to try using their own numbers as input.
When I assign numbers to the variables myself, it works without fail. However, when I use prompt var numberOne = prompt('What is the first number you want to multiply?'); on one variable (with the other being assigned myself)it works. But as soon as I prompt the user for both numbers it won't work. Presumably because a string can be converted to an integer when an operation is performed on it (multiplied by an integer), but it does not seem to work when both are strings.
Adding another line to reset the prompt variable to an integer using parse seems like too much extra. 

var numberOne = prompt('What is the first number you want to multiply?');
var numberTwo = prompt('What is the second number you want to multiply?');
var numberOneInt = parseInt(numberOne);
var numberTwoInt = parseInt(numberTwo);

Is this really the best way to do it?

Mister Jojo
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MsBee
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1 Answers1

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For a prompt, yes, that is pretty much what you want to do. Prompt returns a string, so you need to convert it. There are other ways, i.e. Number(numberOne), but parseInt is fine. They have slightly different behaviors, but for your case they're mostly the same. (parseInt stops parsing at the first non-number, while Number type-casting attempts to convert the whole thing).

And kudos for figuring out the edge behavior of having one string and one int multiplied together.

In general, most developers prefer using inputs on the page rather than prompts. The problem with prompts is that they interrupt the user's control of the page. As a bonus, with inputs you can set type=number to give the users number controls on some devices and limit the input to actual numbers.

Edit

I don't ever use prompt, so I was reading up on them. One thing to look out for is if the user hits escape, it returns null, which may break your code. You could prevent that by just checking for it first, i.e. if(numberOne){ ... }

tmdesigned
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  • So, that worked. thank you. I'm trying to make sure I use certain in things in this program. For example, white lists, black lists. So, if I know that I can use input to set type, I'm not sure where I'd give use those. I'm going to consider rewriting with input instead, though. I can always use those in other programs. – MsBee Apr 01 '20 at 00:02