regex expression in javascript not working as expected

Question

we are trying to find if the given string is a valid indian mobile number or not

valid indian mobile number

starts with 7 or 8 or 9
followed by 9 same or different numbers

here is my JavaScript for matching it, but unfortunately it returns false even when number is correct

var mobile_number = $('#number').val();
var mobile_regex = new RegExp('/^[789]\d{9}$/');
if(mobile_regex.test(mobile_number) == false) {
    console.log("not valid");
} else {
    console.log("valid");
}

What is a correct number? [https://regex101.com/r/yW6vC2/1](https://regex101.com/r/yW6vC2/1) Here I can see that 7123456789 is a match, for example. Are there any other symbols at the front/back of the number? — Maria Ivanova, Jun 30 '16 at 11:41
@MariaDeleva anything followed by 7,8,9 but length must be equal to 10 — runningmark, Jun 30 '16 at 11:43
@anubhava what is the difference with the current approach? Just wondering: doesn't `RegExp()` allow `\d`? — fedorqui 'SO stop harming', Jun 30 '16 at 11:44
Perhaps, you can try this: `var mobile_regex = new RegExp('^[789]\d{9}$');` — Maria Ivanova, Jun 30 '16 at 11:46
possible duplicate of http://stackoverflow.com/questions/9801630/what-is-the-difference-between-square-brackets-and-parentheses-in-a-regex — Alexander Solonik, Jun 30 '16 at 11:54
@fedorqui: 2 problems. `RegExp` doesn't need regex delimiter `/` and it requires double escaping. — anubhava, Jun 30 '16 at 12:04

score 3 · Answer 1 · answered Jun 30 '16 at 11:48

3

Your code has two problems. If you're using a RegExp object, you don't need / characters, and the \ character needs to be escaped.

This would work:

var mobile_regex = new RegExp("^[789]\\d{9}");

Alternatively, if you want to use the other format, this would work:

if(!mobile_number.match(/^[789]\d{9}/)) {
    console.log("not valid");
} else {
    console.log("valid");
}

answered Jun 30 '16 at 11:48

Chris Lear

6,057
1
14
25

why when using new RegExp does \d need to be escaped. /? – Alexander Solonik Jun 30 '16 at 11:51
It's just the `\ ` that needs to be escaped. The reason is that `\ ` is an escape character in javascript strings. – Chris Lear Jun 30 '16 at 13:59

score 2 · Accepted Answer · answered Jun 30 '16 at 11:42

2

You can try this

   var mobile_number = $('#number').val();
   var mobile_regex = new Regex("^[7-9][0-9]{9}$")
   if(mobile_regex.test(mobile_number) == false) {
   console.log("not valid");
   } else {
    console.log("valid");
   }

answered Jun 30 '16 at 11:42

Nikhil Ghuse

1,218
12
29

regex expression in javascript not working as expected

2 Answers2

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