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<html>
<head>
<style type="text/css">
.container {
position: static;
width: 800px;
height: 350px;
overflow: hidden;
}
.embed {
height: 100%;
width: 100%;
min-width: 1000px;
margin-left: -360px;
margin-top: -57px;
overflow: hidden;
}
body {
width: 800px;
margin: auto;
padding: 1em;
font-family: "Open Sans", sans-serif;
line-height: 150%;
letter-spacing: 0.1pt;
}
img {
width: 90%;
text-align: center;
margin: auto;
box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
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pre, code {
padding: 1em;
}
</style>
<script>
document.addEventListener('readystatechange', event => {
if (event.target.readyState === "complete")
document.activeElement.blur();
});
</script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.18.1/styles/default.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.18.1/highlight.min.js"></script>
</head>
<body>
<h2 id="namedgroups">Named Groups</h2>
<p>Regular expressions with lots of groups and backreferencing can be difficult to maintain, as adding or removing a capturing group in the middle of the regex turns to change the numbers of all the groups that follow the added or removed group.</p>
<p>In regex, we have facility of named groups, which solves the above issue. Let's look at it.</p>
<p>We can name a group by putting <code>?&lt;name&gt;</code> just after opening the paranthesis representing a group. For example, <code>(?&lt;year&gt;\d{4})</code> is a named group.</p>
<p>Below is a code, we have already looked in <strong>capturing groups</strong> part. You can see, the code is more readable now.</p>
<pre><code class="js language-js"> var str = "2020-01-20";
// Pattern string
var pattern = /(?&lt;year&gt;\d{4})-(?&lt;month&gt;\d{2})-(?&lt;day&gt;\d{2})/g;
// ^ ^ ^
//group-no: 1 2 3
// Data replacement using $&lt;group_name&gt;
var ans=str.replace(pattern, '$&lt;day&gt;-$&lt;month&gt;-$&lt;year&gt;');
console.log(ans);
// Output will be: 20-01-2020
</code></pre>
<p>Backreference syntax for numbered groups works for named capture groups as well. <code>\k&lt;name&gt;</code> matches the string that was previously matched by the named capture group <code>name</code>, which is a standard way to backreference named group.</p>
<div class="container">
<iframe scrolling="no" style="position: absolute; top: -9999em; visibility: hidden;" onload="this.style.position='static'; this.style.visibility='visible';" src="https://regexr.com/4vu8k" class="embed"></iframe>
</div>
<script type="text/javascript">
document.addEventListener('DOMContentLoaded', (event) => {
document.querySelectorAll('pre code').forEach((block) => {
hljs.highlightBlock(block);
});
});
</script>
</body>
</html>