Javascript / jQuery search for letter in string

Question

I'm using JS / jQuery (new to jQuery) and I have a string with a math problem in it, including a variable. (I'm creating a function to solve basic algebra). ie:

var $problem = "x+5=11";
// Take off any whitespace from user input
$problem = $problem.replace(/\s+/g,"");
// Split problem into two parts
$problem = $problem.split("=");

Now I need to determine which part contains the variable. In this example it would be

$problem[0] // This stores "x+5"

What i'm stuck at is that the variable could be any letter, not just x, so I can't just search for x. It could be: a, b, A, x, z, Y.

I hate regex :( It confuses me. But if it's my only option, I must use it! — Vince, Apr 12 '13 at 06:11
what do you want to do with `x+5`? probably you want separate it further to `x` and `5` again — Arun P Johny, Apr 12 '13 at 06:12
@ArunPJohny Yeah, I have the steps for the function written down on paper, that's the next step after determining which part of the array has the variable. For example, I don't event want to try to split the 11 into another array because it only has the one number. — Vince, Apr 12 '13 at 06:14
So you want to check whether LHS or RHS has a variable right? — A J, Apr 12 '13 at 06:14
@AJ Yes. I know how to check if the variable was 'x' all the time, but since it's based on user input, the variable can change. — Vince, Apr 12 '13 at 06:16
that means first you need to find out whether the LHS/RHS has a variable. it can be done via a simple regex test `/[a-zA-Z]+/.test($problem[0])` — Arun P Johny, Apr 12 '13 at 06:17

Arun P Johny · Accepted Answer · 2013-04-12T06:26:27.733

2

You can test for any variable which has an alphabet using the regex

if(/[a-zA-Z$][a-zA-Z$_0-9]*/.test($problem[0])){
    //left part has a variable
}

edited Apr 12 '13 at 06:26

answered Apr 12 '13 at 06:18

Arun P Johny

384,651
66
527
531

common algebra variable names can contain digits too – Ejaz Apr 12 '13 at 06:22
@Ejay in that case we can improve the regex – Arun P Johny Apr 12 '13 at 06:25
@Ejay in js i think vairables can start with an alphabet or `$` – Arun P Johny Apr 12 '13 at 06:27
that's more like programming language variable naming conventions :) He's talking about algebra – Ejaz Apr 12 '13 at 06:42

score 0 · Answer 2 · answered Apr 12 '13 at 06:21

0

'x+5'.split(/[\W]+/g)

'xyx-2a*yb+5'.split(/[\W]+/g)

answered Apr 12 '13 at 06:21

Ejaz

8,719
3
34
49

score 0 · Answer 3 · answered Apr 12 '13 at 06:27

0

You can check if a string has a alphabet in it or not as following:

    var str = "x+1";
    if (str.match(/[a-zA-Z]/g)) {
        alert("true");
        }
    else {

        alert("false");
    }

Hope this helps!

answered Apr 12 '13 at 06:27

A J

2,112
15
24

Javascript / jQuery search for letter in string

3 Answers3