How to search the word and display the matches in given string using javascript?

Html page:

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

Javascript Page:

<script>

function myFunction()

{

    var str = "The rain in SPAIN stays mainly in the plain";

    var res = str.match(/ain/g);

    document.getElementById("demo").innerHTML = res;

}

</script>

Output:

ain,ain,ain

Note:

G for global search its is key word