how to use regular expression in javascript

Question

var pattern=/[A-za-z0-9]/;
if((fs.value||ls.value||ad1.value||ad2.value||pc.value||city.value||email.value)!=pattern)
{alert("fields not entered");
return false;}
else
return true;

Even after entering all the fields in the form, I get alert message "field not entered. Here fs,ls,ad1,ad2,email,pc and city are form field values

You are checking whether the last non-empty value is a regular expression, which will never be the case. Have a you looked at any documentation? developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/… — Felix Kling
– Felix Kling, Commented Apr 21, 2017 at 19:58
This is pretty easy to google ("javascript regexp"), one way is to use str.match(regexp) in your condition. — Spencer Wieczorek
– Spencer Wieczorek, Commented Apr 21, 2017 at 19:59
You can't just compare a string to a regex, you have to run it through a regex tester like ls.value.match(pattern) et al — James
– James, Commented Apr 21, 2017 at 20:00
Simple solution: var fields = [fs, ls, ...]; if (fields.every(f => pattern.test(f.value))) { ... }. — Felix Kling
– Felix Kling, Commented Apr 21, 2017 at 20:03

Shaun Sweet · Accepted Answer · 2017-04-21 20:19:39Z

1

You need to take the values from those fields and run them thru the regex matching tool while passing the regex to that method.

var pattern=/[A-za-z0-9]/;
"string to check against regex pattern".match(pattern);

See more here

answered Apr 21, 2017 at 20:19

Shaun Sweet

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