JavaScript > Regular Expressions Modifiers

Matches string followed by particular character in JavaScript

How to match any string that is followed by a particular character in a specific string in JavaScript?


By using ?= quantifier we can matches any string that is followed by a particular character in a specific string.

EXAMPLE: "ear" followed by "rings".

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

<script>
    function mySearch() {
        var a = "Last year is all were wear rings to their right ear?"
        var b = /ear(?= rings)/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 "Last year is all were wear rings to their right ear? " to the variable a, we can find the the word "ear" in 3 places (year, wear, ear) in a string. But we need to match 'ear' followed by a 'rings' in a string, for that we are using ?= quantifier in the variable b. var b = /ear(?= rings)/g in this ?= quantifier searches in a string where 'ear' is followed by 'rings' with the help of a global search g, and variable r returns the global search result. Onclick of the button "Search" in HTML code fires the function mySearch() in the <script> block at the same time ?= quantifier do the global search for the word 'ear' followed by 'rings' in a string and returns 'ear' from the word 'wear' as a output.

OUTPUT

 

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