How to match a string against an array of pattern in Javascript?

Question

I've two variables:

var input = "user1@gmail.com";
var preferredPatterns = ["*@gmail.com", "*@yahoo.com", "*@live.com"];

Want to match the input with preferred pattern array. If any of the patterns matches I've to do certain task (in this example, input is a definite match). How can I match against an array of pattern in javascript?

What kind of patterns are those? Those are not regular expressions. — Felix Kling, Apr 06 '15 at 07:07
You need to take every and rewrite. Do you know regular expressions syntax? — zerkms, Apr 06 '15 at 07:11

score 9 · Answer 1 · answered Apr 06 '15 at 07:18

9

You can compile your patterns (if they are valid regular expressions) into one for performance:

var masterPattern = new RegExp(patterns.join('|'));

Putting it all together:

var input = 'user1@gmail.com';
var preferredPatterns = [
  ".*@gmail.com$",
  ".*@yahoo.com$",
  ".*@live.com$"
];

var masterPattern = new RegExp(preferredPatterns.join('|'));

console.log(masterPattern.test(input));
// true

answered Apr 06 '15 at 07:18

Amadan

191,408
23
240
301

That was not a part of the question. If you want that, you're better off going with @AvinashRaj's solution. This will only find whether or not any of the pattern matches, as per your original question, very very fast. (Handcrafting the `masterPattern` would be even faster, as you can refactor the `.* -- $` bit for more speed). – Amadan Apr 06 '15 at 07:21
but this one shows `SyntaxError: Invalid regular expression: /*@qa-server5.com$|*@qa-server4.com$/` – fatCop Apr 06 '15 at 08:36
"if they are valid regular expressions". Yours are not - there needs to be a period in front of the `*`. If you want to allow your users to input patterns, then you also need a method to transform them into valid regular expressions (escaping any dangerous characters, and turning `*` into `.*`, for starters). Otherwise, just write correct regular expression patterns in the first place. – Amadan Apr 06 '15 at 08:38

score 4 · Accepted Answer · edited Apr 06 '21 at 05:45

4

You need to use RegExp constructor while passing a variable as regex.

var input = 'user1@gmail.com';
var preferredPatterns = [".*@gmail\\.com$", ".*@yahoo\\.com$", ".*@live\\.com$"];
for (i=0; i < preferredPatterns.length;i++) {
  if(input.match(RegExp(preferredPatterns[i]))) {
     console.log(preferredPatterns[i])
    }
    }

Dot is a special meta-character in regex which matches any character. You need to escape the dot in the regex to match a literal dot.

As @zerkms said, you could use the below list of patterns also.

var preferredPatterns = ["@gmail\\.com$", "@yahoo\\.com$", "@live\\.com$"];

edited Apr 06 '21 at 05:45

marc_s

732,580
175
1,330
1,459

answered Apr 06 '15 at 07:12

Avinash Raj

172,303
28
230
274

you mean that i need to give an exact pattern to match email id? – Avinash Raj Apr 06 '15 at 07:13
No, I mean that you can remove `.*` from regular expressions and nothing will change. – zerkms Apr 06 '15 at 07:14
1

Use dot before star in your Regex. Please recheck the Regex I used. – Avinash Raj Apr 06 '15 at 08:44
.* will match all the characters including space. So we should use non space character \S i.e. ["\\S*@gmail\\.com", "\\S*@yahoo\\.com", "\\S*@live\\.com"] – Hussain KMR Behestee Feb 25 '19 at 05:15

score 1 · Answer 3 · answered Apr 06 '15 at 07:27

Try this helper function:

/**
 * Returns an integer representing the number of items in the patterns 
 * array that contain the target string text
 */
function check(str, patterns) {
   return patterns.reduce(function (previous, current) {
      return previous + (str.indexOf(current) == -1 ? 0 : 1);
    }, 0);
}

check("user@gmail.com", ["@gmail.com", "@yahoo.com", "@live.com"]; // returns 1
check("user@live.com", ["@gmail.com", "@yahoo.com", "@live.com"]; // returns 0

score 1 · Answer 4 · edited May 23 '17 at 12:09

If you want a general approach to matching against a list of regular expressions then some version of Avinash Raj's answer will work.

Based on the fact that you are specifying certain domains, you might want to match any valid email address using the regex here, and if it matches then check if the domain is a preferred one. There are a number of different ways you could do that of course. Here's just a simple example, splitting on the @ and using jQuery.inArray() to check if the domain is preferred.

var preferredDomains = ["gmail.com", "yahoo.com", "live.com"];

function isValid(inputVal) {
    var re = /^([\w-]+(?:\.[\w-]+)*)@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$/i;

    return re.test(inputVal) && $.inArray(inputVal.split('@')[1], preferredDomains) > -1;
}

The advantage here is that the underlying regex doesn't change, just the much easier to read/maintain list of domains. You could tweak this to capture the domain in a group, instead of using split().

score 0 · Answer 5 · edited Apr 06 '21 at 05:45

0

preferredPatterns.forEach(function(element, index){ 
   if(input.match('/'+element) != null){ 
      console.log('matching  ' + element)  
   }
})

you can write your custom logic if a string matches any pattern.

edited Apr 06 '21 at 05:45

marc_s

732,580
175
1,330
1,459

answered Apr 06 '15 at 07:29

Nirav Shah

67
1
2

score 0 · Answer 6 · edited Apr 06 '21 at 05:45

No regexp you may do as follows;

function matchPattern(xs, [y,...ys]){
  
  function helper([x,...xs]){
    return "*" + xs.join('') === y ? true
                                   : xs.length ? helper(xs)
                                               : false;
  }
  
  return helper(xs) ? y
                    : ys.length ? matchPattern(xs,ys)
                                : "No Match..!";
}

var input             = "user1@gmail.com",
    preferredPatterns = ["*@yahoo.com", "*@live.com", "*@gmail.com"];
    result            = matchPattern(input, preferredPatterns);

console.log(result);

score -2 · Answer 7 · answered Apr 06 '15 at 07:15

-2

You may iterate through array and then use regex to compare with individual items.

answered Apr 06 '15 at 07:15

Bhisham Balani

228
1
4

How to match a string against an array of pattern in Javascript?

7 Answers7