How to create a regex that checks the string contains specific pattern in javascript?

Question

I have a requirement where I need to traverse through the string and get the first occurrence of a specific pattern like as follows,

i am a new **point**

On the occurrence of two consecutive character it must return true.

I must *not* be returned or*

The above pattern must return false.I tried to create regex following few links but the string.match method always returns null. My code,

var getFormat = function(event) {
  var element = document.getElementById('editor');
  var startIndex = element.selectionStart;
  var selectedText = element.value.slice(startIndex);
  var regex = new RegExp(/(\b(?:([*])(?!\2{2}))+\b)/)
  var stringMatch = selectedText.match(regex);
  console.log('stringMatch', stringMatch);

}

<html>

<body>

  <textarea onclick='getFormat(event);' rows='10' cols='10' id='editor'></textarea>
</body>

</html>

As I am new to regex I couldn't figure out where I am wrong.Could anyone help me out with this one?

vallentin · Accepted Answer · 2017-04-25 04:25:04Z

1

On the occurrence of two consecutive character it must return true.

If I'm understanding you correctly. You just want to check if a string contains two consecutive characters, no matter which character. Then It should be enough doing:

(.)\1

Live Demo

This is of course assuming that it's literally any character. As in two consecutive whitespaces also being a valid match.

If you just need to check if there's two stars after each other. Then you don't really need regex at all.

s = "i am a new **point**";

if (s.indexOf("**") != -1)
    // it's a match

If it's because you need the beginning and end of the two stars.

begin = s.indexOf("**");
end = s.indexOf("**", begin + 1);

Which you with regex could do like this:

((.)\2)(.*?)\1

Live Demo

edited Apr 25, 2017 at 4:25

answered Apr 25, 2017 at 4:19

vallentin

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2 Comments

akila arasan Over a year ago

I have to check whether the string is bounded by ** or _ .If is bounded by these special characters alone it must return true.

vallentin Over a year ago

Bounded? Do you mean whether there's two sets before and after something? Because if so I just added something in relation to that.

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