Regex to match three or more of the same char regardless of its position

Question

Looking for a regular expression in PHP or javaScript that return true if 3 or more of the same characters (regardless of its 'position') are found:

    "q6dqaqb" -> return true
    "qyakc6m" -> return false
    "jjfffua" -> return true
    "--rr4-c" -> return true
    "-qsev-m" -> return false

I have tried to the best of my ability to search for a solution like this

( Regular expression: same character 3 times )

but this does not fit the requirement.

Edit:Thank you all for the swift reply. The PHP solution is awesome too.

Based on the answers, What is the difference between these regex:

(.)(?=.*\1.*\1)

.*(.).*\1.*\1.*

(?=.*(.).*\1.*\1)

Sorry, I can't live with myself until I understand what it means.

Answer 1

使用先行查找三个中的第一个：

/(.)(?=.*\1.*\1)/

Answer 2

This expression

(?=.*(.).*\1.*\1)

might likely ensure that and to get the entire string, we can expand it to:

^(?=.*(.).*\1.*\1).*$

Demo

Test

$re = '/^(?=.*(.).*\1.*\1).*$/m';
$str = 'q6dqaqb
qyakc6m
jjfffua
--rr4-c
-qsev-m
';

preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);

var_dump($matches);

Output

array(3) {
  [0]=>
  array(2) {
    [0]=>
    string(7) "q6dqaqb"
    [1]=>
    string(1) "q"
  }
  [1]=>
  array(2) {
    [0]=>
    string(7) "jjfffua"
    [1]=>
    string(1) "f"
  }
  [2]=>
  array(2) {
    [0]=>
    string(7) "--rr4-c"
    [1]=>
    string(1) "-"
  }
}

 const regex = /^(?=.*(.).*\\1.*\\1).*$/gm; const str = `q6dqaqb qyakc6m jjfffua --rr4-c -qsev-m `; let m; while ((m = regex.exec(str)) !== null) { // This is necessary to avoid infinite loops with zero-width matches if (m.index === regex.lastIndex) { regex.lastIndex++; } // The result can be accessed through the `m`-variable. m.forEach((match, groupIndex) => { console.log(`Found match, group ${groupIndex}: ${match}`); }); } 

Answer 3

You can try this /(.).*\\1.*\\1/ .

Demo:

 var regex = /(.).*\\1.*\\1/; console.log(regex.test("q6dqaqb")) console.log(regex.test("qyakc6m")) console.log(regex.test("jjfffua")) console.log(regex.test("--rr4-c")) console.log(regex.test("-qsev-m"))