Javascript - How would you regex this pattern. Can't seem to do it

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Get query string values in JavaScript

I "had" this pattern but it didn't quite give me what I need, though it worked.

var regex = new RegExp('\\b' + data.keyword + '(=[^&]*)?(&|$)',"gi");

But the following regular expressions "is" what I need but i can't seem to get it to work within the regex obj: /&dyanmicTxtHere(\=[^&])?(?=&|$)|^dyanmicTxtHere(\=[^&])?(&|$)/

I tried: This is NOT working -

var regex = new RegExp('&' + data.keyword + '(=[^&]*)?|^' + data.keyword + '(=[^&]*)?&?',"gi");

I can't figure out why. So the above regex should strip out my passed param (and vlaue)(data.keyword), and deal with the ? and & wherever that param sits in the url. It

So, what would this match?

www.someurl.com?Keyword=foo

www.someurl.com?up=down&Keyword=foo

www.somurl.com?up=down&keyword=foo&left=right

etc... so, if I passed in "Keyword" as my dynamic param, then it would remove it and its associated value.

Why would someone DOWN VOTE my question? Was it phrased inappropriately? Not enough info? Kinda lame.. — james emanon, Aug 28 '12 at 18:26
Then that isn't fair as this isn't about getting values, that is easy (imho). This is a regex to delete a particular name & value from a url. — james emanon, Aug 28 '12 at 21:02

score 3 · Answer 1 · edited May 23 '17 at 12:12

3

Looks to me that what you want is to read parameter values from a request, via JavaScript, correct?

Try using this:

function getParameterByName(name)
{
    name = name.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");
    var regexS = "[\\?&]" + name + "=([^&#]*)";
    var regex = new RegExp(regexS);
    var results = regex.exec(window.location.search);
    if(results == null)
        return "";
    else
        return decodeURIComponent(results[1].replace(/\+/g, " "));
}

Taken from this question.

edited May 23 '17 at 12:12

Community

1
1

answered Aug 28 '12 at 18:06

Apoc

88
1
6

I don't really want to "read" the params, I want to be able to delete one and its value. The one I want to delete could be dynamically decided. So, I pass in my paramToDelete and my regex (posted above) will strip it and its value. – james emanon Aug 28 '12 at 18:13
So you could easily rebuild the query string by reading all parameters minus the one you want to exclude. In the question I linked, there are other functions that retrieve all parameters at once. – Apoc Aug 28 '12 at 18:17

score 1 · Answer 2 · answered Aug 28 '12 at 18:10

If you need to see what the produced regex looks like, simply call regex.toString()

If you do that on the one you tried you get:

/&dyanmicTxtHere(=[^&]*)?|^dyanmicTxtHere(=[^&]*)?&?/gi

Based on that, you can fairly see what needs changing to make it like the regex you provided:

var regex = new RegExp('&' + data.keyword + '(\\=[^&])?(?=&|$)|^' + data.keyword + '(\\=[^&])?(&|$)', '');

If we call toString on that we get:

/&dyanmicTxtHere(\=[^&])?(?=&|$)|^dyanmicTxtHere(\=[^&])?(&|$)/

If that doesn't work, try explaining exactly what you're trying to parse.

score 1 · Accepted Answer · answered Aug 28 '12 at 18:47

Obviously what follows is not a regular expression; but it should, I think, fulfil your requirements. It takes advantage of the requirements of name-value pairs in a GET query-string, and uses simple string, and some array, manipulation to examine the various (if any) name-value pairs from the passed URL:

function removeParam(url, param) {
    // checks for the existence of a '?' in the passed url:
    var queryAt = url.indexOf('?') + 1;
    /* function exits if:
       1. no 'url' parameter was passed,
       2. no 'param' parameter was passed in, or
       3. the 'queryAt' variable is false, or has a falsey value */
    if ((!url || !param) || !queryAt) {
        return false;
    }
    else {
        /* if the 'param' passed in wasn't found in the 'url' variable,
           the function exits, returning the original url (as no modification
           is required */
        if (url.indexOf(param) == -1) {
            return url;
        }
        else {
                /* gets the substring of the url from the first
                   character *after* the '?' */
            var all = url.substring(queryAt),
                // creates an array of the name and value pairs
                nameValues = all.split('&'),
                // creating a new array
                newNameValues = [],
                parts;
            // iterates through each name-value pair
            for (var i = 0, len = nameValues.length; i < len; i++) {
                // splits the name-value pair into two parts
                parts = nameValues[i].split('=');
                /* if the first part (the 'name' of the param) does not
                   matches what you're looking for then the whole name-value
                   pair is pushed into the 'newNameValues' array */
                if (parts[0] !== param) {
                    newNameValues.push(nameValues[i]);
                }
            }
            // returns the reconstructed URL
            return url.substring(0, queryAt) + newNameValues.join('&');
        }
    }
}

JS Fiddle demo.

Javascript - How would you regex this pattern. Can't seem to do it

3 Answers3