Check if element contains any of the class from array

Question

I have the following elements:

Answer 1

No need of loop over each of the element and each of the class to check it it exists on the element.

You can use regex as follow:

Demo

var arr = ['nine', 'ten', 'eleven'];
var classes = '\\b(' + arr.join('|') + ')\\b',
  regex = new RegExp(classes, 'i');


$('div').each(function() {
  var elClasses = ' ' + $(this).attr('class').replace(/\s+/, ' ') + ' ';
  if (regex.test(elClasses)) {
    $(this).addClass('valid');
  }
})

div {
  color: red;
}
.valid {
  color: green;
}

Invalid
Valid Ten
Invalid
Invalid
Valid 11
Valid 9

REGEX EXPLANATION

1. \b: Will match the word boundary
2. |: Works as OR in regex
3. arr.join('|'): Will join all the elements of array using | to join
4. (): Capturing Group. In this case used for matching one of the class

So, regex in above case will be

/\b(nine|ten|eleven)\b/