RegEx - JavaScript .match() with a variable keyword

Question

I have a string with keywords, separated by comma's.

Now I also have a nice RegEx, to filter out all the keywords in that string, that matches a queried-string.

Check out this initial question - RegEx - Extract words that contains a substring, from a comma seperated string

The example below works fine; it has a masterString, and a resultString. That last one only contains the keywords that has at least the word "car" in it.

masterString = "typography,caret,car,align,shopping-cart,adjust,card";
resultString = masterString.match(/[^,]*car[^,]*/g);
console.log(resultString);

Result from the code above;

"caret", "car", "shopping-cart", "card"

But how can I use the RegEx, with a variable matching-word (the word "car" in this example static and not variable).

I think it has to do something with a RegExp - but I can't figure out...

developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — Qantas 94 Heavy
– Qantas 94 Heavy, Commented Aug 2, 2014 at 14:02
Rather than define a new RexExp with a string where you have to replace |QUERY| with something, why not just do string concatenation? That's how the RegExp object was meant to be used. — RevanProdigalKnight
– RevanProdigalKnight, Commented Aug 2, 2014 at 15:28
Thx - I added another solution (#2) which does the job, as you said! — El Bandito
– El Bandito, Commented Aug 2, 2014 at 15:38
@ElBandito try typing something like he(]o in your search box :) — Lucas Trzesniewski
– Lucas Trzesniewski, Commented Aug 2, 2014 at 15:42
@LUCAS - yeah :) But I also cleaned up the query, after submitting and before validating... See the code I used for that overhere... i.imgur.com/zC0NzRd.jpg In my case it's safe to use this solution, because it's used in an app, with little user-control (I control all the codes and there behaviour). — El Bandito
– El Bandito, Commented Aug 2, 2014 at 16:34

Lucas Trzesniewski · Accepted Answer · 2014-08-02 14:50:34Z

2

Here's a general solution for use with regexes:

var query = "anything";    

// Escape the metacharacters that may be found in the query
// sadly, JS lacks a built-in regex escape function
query = query.replace(/[-\\()\[\]{}^$*+.?|]/g, '\\$&');

var regex = new RegExp("someRegexA" + query + "someRegexB", "g");

As long as someRegexA and someRegexB form a valid regex with a literal in-between, the regex variable will always hold a valid regex.

But, in your particular case, I'd simply do this:

var query = "car";
var items = masterString.split(",");
query = query.toLowerCase();
for (var i = 0; i < items.length; ++i) {
    if (items[i].toLowerCase().indexOf(query) >= 0) {
        console.log(items[i]);
    }
}

edited Aug 2, 2014 at 14:50

answered Aug 2, 2014 at 14:45

Lucas Trzesniewski

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Comments

Will · Accepted Answer · 2014-08-02 14:43:47Z

1

How about this one?, you only need to replace \ \ with String , and it works for me. it can find whether your string has "car", not other similar word

 var query  = 'car';
 var string = "car,bike,carrot,plane,card";
 var strRegEx = '[^,]*'+query+'[,$]*'; 
 string.match(strRegEx);

answered Aug 2, 2014 at 14:43

Will

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1 Comment

El Bandito Over a year ago

I picked this one as the answer, because it comes closest to the one I figured out myself (see Update 2). But the other solution on this page is very good as well; They both do their job - thx!

brasofilo · Accepted Answer · 2018-08-04 01:00:40Z

0

^{_{Answer provided by OP and removed from inside the question}}

I figured out this quick-and-maybe-very-dirty solution...

var query  = 'car';
var string = "car,bike,carrot,plane,card";
var regex  = new RegExp("[^,]*|QUERY|[^,]*".replace('|QUERY|',query),'ig');
string.match(regex);

This code outputs the following, not sure if it is good crafted, 'though..

"car", "carrot", "card"

But ended figuring out another, much simpler solution;

var query  = "car";
var string = "car,bike,carrot,plane,card";
string.match(new RegExp("[^,]*"+query+"[^,]*",'ig'));

This code outputs the string below;

["car", "carrot", "card"]

My app-search-engine now works perfect :)

answered Aug 4, 2018 at 1:00

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