Javascript regex match only words starting with a specific special character

Question

I'm trying to match only words starting with # in javascript, for eg. in the following sample text, only #these should match.

I need to match only words like #these. Ignore the ones like @#this , !#this and in#ignore.

The closer I got is here,

/(\B(#[a-z0-9])\w+)/gi

Ref: https://regex101.com/r/wU7sQ0/114

Answer 1

Use a whitespace boundary (?:^|\s):

var rx = /(?:^|\s)(#[a-z0-9]\w*)/gi;
var s = "I need to match only words like #these. \nIgnore the ones like @#this , !#this and in#ignore.";
var m, res=[];
while (m = rx.exec(s)) {
  res.push(m[1]);
}
console.log(res);

Details:

• (?:^|\s) - matches the start of string or whitespace
• (#[a-z0-9]\w*) - Group 1 (m[1]): a #, then an alphanumeric char followed with 0 or more word chars (letters, digits, _ symbols).

See the regex demo, pay attention to what texts are captured, rather to the whole matches.

Or trimming each match:

var rx = /(?:^|\s)(#[a-z0-9]\w*)/gi;
var s = "I need to match only words like #these. \nIgnore the ones like @#this , !#this and in#ignore.";
var results = s.match(rx).map(function(x) {return x.trim();}); // ES5
// var results = s.match(rx).map(x => x.trim()); // ES6
console.log(results);