How to check if value is in preferd format

Question

i have a input field.

Inside this field the user should only enter text in this format

1+1+2+3

maximum 1+1+1+1+1+1+1+1+1+1+1+1 (12x)

How i can check this only checking for numbers var isnum = /^\d+$/.test($(this).val()); will be the half work, but for more i dont know how...

Relying on users to enter data in a specific format is asking for trouble. I'd suggest either using individual input elements for each number, or a masking library to restrict the input options. — Rory McCrossan, Feb 13 '19 at 11:09
yes only digits and plus-sign and the maximum of entered numbers must be = 12, 6+6 or 3+6+3... — MikeR, Feb 13 '19 at 11:14

T.J. Crowder · Accepted Answer · 2019-02-13T11:52:12.027

4

You can use a quantifier to say how many to accept, so:

var isnum = /^\d+(?:\+\d+){0,11}$/.test($(this).val());

That says to accept any number of digits at the beginning, optionally followed by 0 to 11 examples of + and any number of digits.

Live Example:

function test(str, expect) {
  var result = /^\d+(?:\+\d+){0,11}$/.test(str);
  console.log(str, result, !result === !expect ? "Test:Pass" : "Test:FAIL");
}

test("1", true);
test("1+2+3+4+1234", true);
test("1+1+1+1+1+1+1+1+1+1+1+1", true);
test("1+1+1+1+1+1+1+1+1+1+1+1+1", false);

In a comment you've added:

es only digits and plus-sign and the maximum of entered numbers must be = 12, 6+6 or 3+6+3...

That's a completely different thing, and you can't reasonably test for it with a regular expression (you'd need a ridiculous number of alternatives). Instead, use a regular expression (such as the above) to test the format, then do the sum:

if (/*...the format is good...*/) {
    sum = str.split("+").reduce((a, b) => Number(a) + Number(b));
    if (sum > 12) {
        // disallow it
    }
}

Live Example:

function test(str, expect) {
  var result = /^\d+(?:\+\d+){0,11}$/.test(str);
  if (result) {
    result = str.split("+").reduce((a, b) => Number(a) + Number(b)) <= 12;
  }
  console.log(str, result, !result === !expect ? "Test:Pass" : "Test:FAIL");
}

test("1", true);
test("1+2+3+4+1234", false); // sum > 12
test("1+1+1+1+1+1+1+1+1+1+1+1", true);
test("1+1+1+1+1+1+1+1+1+1+1+1+1", false); // too many
test("12345", false); // sum > 12

In that I've used Number(x) to convert from string to number, but you have a lot of options, which I detail in this answer.

edited Feb 13 '19 at 11:52

answered Feb 13 '19 at 11:08

T.J. Crowder

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he is talking about the sum ( 12 ) – Pranav C Balan Feb 13 '19 at 11:15
@PranavCBalan - ***sigh*** :-) – T.J. Crowder Feb 13 '19 at 11:15
probably `eval()` can be use – Pranav C Balan Feb 13 '19 at 11:16
@PranavCBalan - Yeah, but I opted for `split` and `reduce`. :-) – T.J. Crowder Feb 13 '19 at 11:18
yes, that would be better than eval :) , improper use may cause issues. – Pranav C Balan Feb 13 '19 at 11:19
you have to parse string into num – Pranav C Balan Feb 13 '19 at 11:20
`sum = str.split("+").reduce((a, b) => a + +b, 0);` – Pranav C Balan Feb 13 '19 at 11:20
@T.J.Crowder thanks for explaining, one thing, if i enter "12345" it should failed, but i will accept - how i have to change the regex – MikeR Feb 13 '19 at 11:36
@MikeR - With the above, entering `12345` fails (because the sum is > 12). If you mean you want just the regular expression to reject it, what makes it not fit? Is a `+` always required? – T.J. Crowder Feb 13 '19 at 11:52
oh sorry, to make it a little complicate. in case entering only 12 it is ok, enter more than 12 is not ok,enter more than 12 in sum of each seperated numbers by plus-sign is also not ok. And we need everytime exactly 12 – MikeR Feb 13 '19 at 12:03
1

@MikeR *"And we need everytime exactly 12"* Well, that's new information. You can easily work out how to change the above to do that, though, surely? `sum > 12` => `sum !== 12`? – T.J. Crowder Feb 13 '19 at 12:06

How to check if value is in preferd format

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