javascript regex pattern with an array

Question

I want to create a regex pattern which should be able to search through an array.

Let's say :

var arr = [ "first", "second", "third" ];
var match = text.match(/<arr>/);

which should be able to match only

<first> or <second> or <third> ......

but should ignore

<ffirst> or <dummy>

I need an efficient approach please .

Any help would be great . Thanks

• djadmin: I want to match tags which are enclosed within angular brackets and highlight them but the text inside brackets should be in the array.

Answer 1

1. First you can do array.map to quote all special regex characters.
2. Then you can do array.join to join the array elements using | and create an instance of RegExp.

Code:

function quoteSpecial(str) { return str.replace(/([\[\]^$|()\\+*?{}=!.])/g, '\\1ドル'); }
var arr = [ "first", "second", "third", "fo|ur" ];
var re = new RegExp('<(?:' + arr.map(quoteSpecial).join('|') + ')>');
//=> /<(?:first|second|third|fo\|ur)>/

then use this RegExp object:

'<first>'.match(re); // ["<first>"]
'<ffirst>'.match(re); // null
'<dummy>'.match(re); // null
'<second>'.match(re); // ["<second>"]
'<fo|ur>'.match(re); // ["<fo|ur>"]

• anubhava: You're welcome, and a great question +1. And sorry I got a call in between to could not submit desired edit in time.

Answer 2

You should search for a specific word from a list using (a|b|c).

The list is made from the arr by joining the values with | char as glue

var arr = [ "first", "second", "third" ];
var match = text.match(new RegExp("<(?:"+arr.join("|")+")>")); //matches <first> <second> and <third>

Note that if your "source" words might contain regular expression's preserved characters - you might get into trouble - so you might need to escape those characters before joining the array

A good function for doing so can be found here:

function regexpQuote(str, delimiter) {
 return String(str)
 .replace(new RegExp('[.\\\\+*?\\[\\^\\]$(){}=!<>|:\\' + (delimiter || '') + '-]', 'g'), '\\$&');
}

so in this case you'll have

function escapeArray(arr){
 var escaped = [];
 for(var i in arr){
 escaped.push(regexpQuote(arr[i]));
 }
 return escaped;
}
var arr = [ "first", "second", "third" ];
var pattern = new RegExp("<(?:"+escapeArray(arr).join("|")+")>");
var match = text.match(pattern); //matches <first> <second> and <third>

• Thomas Urban: Don't forget to ensure arr isn't containing | and similar functional characters before compiling this way.