Matching sequence of numbers in JavaScript

How to match any string that contains a sequence of X (Digit) from specified digits in a string in JavaScript?

By using d{X} quantifier we can match any string that contains a sequence of X from specified digits in a string.

NOTE:

\d is the Metacharacter, which is used to find a digit.
{X} is the input value and it must be a number.

<p>Click the below button to match a sequence of numbers.</p>
<input type="button" value="Click" onclick="mySearch()" />
<p id="myId"></p>

<script>
    function mySearch() {
        var a = "5252, 45286, 621522, 7845251";
        var b = /\d{3}/g;
        var r = a.match(b);
        document.getElementById("myId").innerHTML = r;
    }
</script>

In the above code snippet we have given Id as "myId"to the second <p> element in the HTML code. There is a function mySearch() in the<script>block which is connected to the onclick of the HTML button and there is a string with value "5252, 45286, 621522, 7845251" to the variable a, we need to match any string that contains a sequence of X from a specified digits, for that we are using d{X} quantifier in variable b. var b = /\d{3}/g here \d is the metacharacter for finding a digit, 3 is the input character for matching a 3-digit sequence of numbers and g do the global search in a string, varaible r returns the matched sequence result. Onclick of the button "Click" in the HTML code fires the function mySearch() in the <script> block at the same time d{X} quantifier matches any string that contains a sequence of X (X=3) in a string with the help of global search g and gives the output.