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 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
– Maria Ivanova, Commented Jun 30, 2016 at 11:41
@MariaDeleva anything followed by 7,8,9 but length must be equal to 10 — runningmark
– runningmark, Commented Jun 30, 2016 at 11:43
@anubhava what is the difference with the current approach? Just wondering: doesn't RegExp() allow \d? — fedorqui
– fedorqui, Commented Jun 30, 2016 at 11:44
@fedorqui: 2 problems. RegExp doesn't need regex delimiter / and it requires double escaping. — anubhava
– anubhava, Commented Jun 30, 2016 at 12:04

Chris Lear · Accepted Answer · 2016-06-30 11:48:09Z

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, 2016 at 11:48

Chris Lear

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2 Comments

Alexander Solonik Over a year ago

why when using new RegExp does \d need to be escaped. /?

Chris Lear Over a year ago

It's just the \ that needs to be escaped. The reason is that \ is an escape character in javascript strings.

Nikhil Ghuse · Accepted Answer · 2016-06-30 11:42:35Z

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, 2016 at 11:42

Nikhil Ghuse

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