Use javascript regex to validate mobile number

Question

The following is my code:

<html>
<title>Validate Phone Number</title>
<head>
<script>
function testnumber() {
    var ph = new RegExp("^[789]\d{9}$");
    num = {10 digit phone number}
    alert(ph.test(num));
}
testnumber();
</script>
</head>
<body>
</body>
</html>

I want to validate mobile phone number which starts with 7/8/9 and is 10 digit. But it alerts false for any phone number given as input.

Please tell me where am I going wrong. Thanks in advance.

I think you'll find a regex tester very useful like [this one for exemple](https://regex101.com/) — 3Dos, Oct 31 '17 at 10:37
@3Dos The tester gives me string matched. But getting false alerted in code for same input — Yash Parekh, Oct 31 '17 at 10:39
To define a ``\`` in a string literal, you must use two backslashes. A too common problem. — Wiktor Stribiżew, Oct 31 '17 at 10:49

Kwesi · Accepted Answer · 2017-10-31T10:58:20.950

2

Try this, your formatting was slightly off:

function testnumber() {
    var ph = new RegExp(/^[789]\d{9}$/);
    num = 7123435498; // example number
    alert(ph.test(num));
}
testnumber();

edited Oct 31 '17 at 10:58

answered Oct 31 '17 at 10:37

Kwesi

607
1
9
21

This worked. (y) Thanks – Yash Parekh Oct 31 '17 at 10:41
1

@YashParekh please mark as correct answer :) – Kwesi Oct 31 '17 at 10:42

Gowtham Shiva · Answer 2 · 2017-10-31T10:49:18.387

1

You can try this HTML only option too

<html>
<body>
<form action="">
 Phone number: <input type="text" pattern="[7-9]{1}[0-9]{9}" title="Enter valid number">
  <input type="submit">
</form>
</body>
</html>

edited Oct 31 '17 at 10:49

answered Oct 31 '17 at 10:45

Gowtham Shiva

3,802
2
11
27

That's cool. Thanks – Yash Parekh Oct 31 '17 at 10:48

gurvinder372 · Answer 3 · 2017-10-31T10:48:25.703

Your existing regex doesn't work for following reason

\d in a string literal is evaluated to d

Hence, you can take following two approaches

1) Try this

var ph = new RegExp("^[789]{1}[0-9]{9}$");
var num = "7894543542";
console.log( ph.test(num) ); //true

^ matches start of the string
[789] matches one of 7,8 or 9
[0-9]{9} matches 9 digits
$ matches end of the string

2) Your regex works fine as well if you passed a regex literal instead of a string.

var ph = new RegExp(/^[789]\d{9}$/);
var num = "7894543542";
ph.test(num); //true

Use javascript regex to validate mobile number

3 Answers3