convert regex string to regex object in javascript

Question

I am getting regex string from json object (yes its dynamic and will be always be string) i want to test this with textbox value.

But even if i pass valid input text it does not pass regex condition

code :

var pattern = "/^[A-Za-z\s]+$/";
var str = "Some Name";
pattern = new RegExp(pattern);
if(pattern.test(str))
{
    alert('valid');
}
else
{
    alert('invalid');
}

Fiddle :- http://jsfiddle.net/wn9scv3m/

Answer 1

Two problems:

• You need to escape the backslash.
• You need to remove the forward slashes on the beginning and end of string.

Corrected code:

var pattern = "^[A-Za-z\\s]+$";
var str = "Some Name";
pattern = new RegExp(pattern);
if(pattern.test(str))
{
    alert('valid');
}
else
{
    alert('invalid');
}

http://jsfiddle.net/wn9scv3m/3/

Answer 2

As far as I can see in https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions you are combining two methods to declare RegExp. If you are using the string variant, then don't include the "/" character before and after the expression, example:

var pattern = "^[A-Za-z\s]+$";
pattern = new RegExp(pattern);

If you like the /regexp/ form better, then use it without quotes:

pattern = /^[A-Za-z\s]+$/;