Performing a simple digit test to a string

Question

I've just started my journey in programming and lately I've been learning how to use JavaScript at University. I am stuck on an exercise that I just cannot get my head around!

The question is: Write a digit test without using logical operators [hint: string operators].

So I need a test to see if there are any digits in a string. I've got as far as:

var x=prompt("Enter any characters"); (e.g. hello123)

var y="0123456789";

(I figured that the input should somehow compare to the y variable so I can get an answer)

That's all I got! Hopefully this shouldn't be too complicated. (Can't wait for that "Oh yeah.." moment!)

Answer 1

I'm not quite sure what the exact bounds of your problem are, but you can use a regular expression to check for digits:

var x = prompt("Enter any characters");
if (x && x.match(/\d/)) {
    // there are digits in the string
}

or written a different way (either is valid):

var x = prompt("Enter any characters");
if (x && /\d/.test(x)) {
    // there are digits in the string
}

Note, this is also making sure that x is non-null and not empty before attempting to use it as a string because if the user cancels the prompt, it will return null.

\d in a regular expression means to match any digit

You can read about regular expressions in javascript here and about the string methods that use them here.

---

I'm still guessing as to what the real bounds of your problem is, but without regex and using only the functions you mention in your comments, you can do this:

var digits = "0123456789";

// get string from user
var str = prompt("Enter any characters");

// check each digit one at a time
if (str) {
    for (var i = 0; i < digits.length; i++) {
        // see if the next digit is in the string
        if (str.indexOf(digits.charAt(i)) {
            // found a digit
        }
    }
}