How to concatenate regex literals in JavaScript ?
Regex is a sequence of pattern that is used for matching with a pattern. While searching for data in a text, the search pattern is described for what we are searching for. It can be a single character or a more complex pattern. It can be used to perform all types of text searches. Regex has its own static and instance properties.
Syntax:
/pattern/modifiers
Example: A regular expression.
/gfg/g
Where,
- gfg is a pattern (to be used in a search).
- g is a modifier (modifies the search to be case-insensitive).
The concatenation of Regex in the programming world can be understood as combining text patterns to obtain a new text pattern, such as “Hello” + “World” is /HelloWorld/. Whenever RegExp() is called, it creates a new RegExp object.
Example 1: This example creating an expression without actually using the Regex literal syntax. This allows you to make arbitrary string manipulation before it becomes a Regex object.
Javascript
function gfg() {
var segment_part = " GeeksforGeeks |"
+ " A computer science portal for geeks" ;
var pattern = new RegExp( "GFG:" +
segment_part +
"is a computer science portal" );
console.log(pattern);
}
gfg();
|
Output:
/GFG: GeeksforGeeks | A computer science portal for geeksis a computer science portal/
Example 2: If you have two Regex literals, you can concatenate them using a technique where it removes duplicates, but keep the unique values in order, joining both the regex literals. Example: /hello/y + / world/g would be /hello world/gy
Javascript
function gfg() {
var regex1 = /geeks/g;
var regex2 = / for geeks/y;
var flags = (regex1.flags +
regex2.flags).split( "" )
.sort().join( "" )
.replace(/(.)(?=.*\1)/g, "" );
var regex3 = new RegExp(regex1.source
+ regex2.source, flags);
console.log(regex3);
}
gfg();
|
Output:
/geeks for geeks/gy
Last Updated :
15 Feb, 2023
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