Parse query string in JavaScript

Question

I need to parse the query string www.mysite.com/default.aspx?dest=aboutus.aspx. How do I get the dest variable in JavaScript?

Answer 1

Here is a fast and easy way of parsing query strings in JavaScript:

function getQueryVariable(variable) {
    var query = window.location.search.substring(1);
    var vars = query.split('&');
    for (var i = 0; i < vars.length; i++) {
        var pair = vars[i].split('=');
        if (decodeURIComponent(pair[0]) == variable) {
            return decodeURIComponent(pair[1]);
        }
    }
    console.log('Query variable %s not found', variable);
}

Now make a request to page.html?x=Hello:

console.log(getQueryVariable('x'));

Answer 2

function parseQuery(queryString) {
    var query = {};
    var pairs = (queryString[0] === '?' ? queryString.substr(1) : queryString).split('&');
    for (var i = 0; i < pairs.length; i++) {
        var pair = pairs[i].split('=');
        query[decodeURIComponent(pair[0])] = decodeURIComponent(pair[1] || '');
    }
    return query;
}

Turns query string like hello=1&another=2 into object {hello: 1, another: 2}. From there, it's easy to extract the variable you need.

That said, it does not deal with array cases such as "hello=1&hello=2&hello=3". To work with this, you must check whether a property of the object you make exists before adding to it, and turn the value of it into an array, pushing any additional bits.

Answer 3

You can also use the excellent URI.js library by Rodney Rehm. Here's how:-

var qs = URI('www.mysite.com/default.aspx?dest=aboutus.aspx').query(true); // == { dest : 'aboutus.aspx' }
    alert(qs.dest); // == aboutus.aspx

---

And to parse the query string of current page:-

var $_GET = URI(document.URL).query(true); // ala PHP
    alert($_GET['dest']); // == aboutus.aspx 

Answer 4

Me too! http://jsfiddle.net/drzaus/8EE8k/

(Note: without fancy nested or duplicate checking)

deparam = (function(d,x,params,p,i,j) {
return function (qs) {
    // start bucket; can't cheat by setting it in scope declaration or it overwrites
    params = {};
    // remove preceding non-querystring, correct spaces, and split
    qs = qs.substring(qs.indexOf('?')+1).replace(x,' ').split('&');
    // march and parse
    for (i = qs.length; i > 0;) {
        p = qs[--i];
        // allow equals in value
        j = p.indexOf('=');
        // what if no val?
        if(j === -1) params[d(p)] = undefined;
        else params[d(p.substring(0,j))] = d(p.substring(j+1));
    }

    return params;
};//--  fn  deparam
})(decodeURIComponent, /\+/g);

And tests:

var tests = {};
tests["simple params"] = "ID=2&first=1&second=b";
tests["full url"] = "http://blah.com/?third=c&fourth=d&fifth=e";
tests['just ?'] = '?animal=bear&fruit=apple&building=Empire State Building&spaces=these+are+pluses';
tests['with equals'] = 'foo=bar&baz=quux&equals=with=extra=equals&grault=garply';
tests['no value'] = 'foo=bar&baz=&qux=quux';
tests['value omit'] = 'foo=bar&baz&qux=quux';

var $output = document.getElementById('output');
function output(msg) {
    msg = Array.prototype.slice.call(arguments, 0).join("\n");
    if($output) $output.innerHTML += "\n" + msg + "\n";
    else console.log(msg);
}
var results = {}; // save results, so we can confirm we're not incorrectly referencing
$.each(tests, function(msg, test) {
    var q = deparam(test);
    results[msg] = q;
    output(msg, test, JSON.stringify(q), $.param(q));
    output('-------------------');
});

output('=== confirming results non-overwrite ===');
$.each(results, function(msg, result) {
    output(msg, JSON.stringify(result));
    output('-------------------');
});

Results in:

simple params
ID=2&first=1&second=b
{"second":"b","first":"1","ID":"2"}
second=b&first=1&ID=2
-------------------
full url
http://blah.com/?third=c&fourth=d&fifth=e
{"fifth":"e","fourth":"d","third":"c"}
fifth=e&fourth=d&third=c
-------------------
just ?
?animal=bear&fruit=apple&building=Empire State Building&spaces=these+are+pluses
{"spaces":"these are pluses","building":"Empire State Building","fruit":"apple","animal":"bear"}
spaces=these%20are%20pluses&building=Empire%20State%20Building&fruit=apple&animal=bear
-------------------
with equals
foo=bar&baz=quux&equals=with=extra=equals&grault=garply
{"grault":"garply","equals":"with=extra=equals","baz":"quux","foo":"bar"}
grault=garply&equals=with%3Dextra%3Dequals&baz=quux&foo=bar
-------------------
no value
foo=bar&baz=&qux=quux
{"qux":"quux","baz":"","foo":"bar"}
qux=quux&baz=&foo=bar
-------------------
value omit
foo=bar&baz&qux=quux
{"qux":"quux","foo":"bar"}   <-- it's there, i swear!
qux=quux&baz=&foo=bar        <-- ...see, jQuery found it
-------------------

Answer 5

Here's my version based loosely on Braceyard's version above but parsing into a 'dictionary' and support for search args without '='. In use it in my JQuery $(document).ready() function. The arguments are stored as key/value pairs in argsParsed, which you might want to save somewhere...

'use strict';

function parseQuery(search) {

    var args = search.substring(1).split('&');

    var argsParsed = {};

    var i, arg, kvp, key, value;

    for (i=0; i < args.length; i++) {

        arg = args[i];

        if (-1 === arg.indexOf('=')) {

            argsParsed[decodeURIComponent(arg).trim()] = true;
        }
        else {

            kvp = arg.split('=');

            key = decodeURIComponent(kvp[0]).trim();

            value = decodeURIComponent(kvp[1]).trim();

            argsParsed[key] = value;
        }
    }

    return argsParsed;
}

parseQuery(document.location.search);

Answer 6

Following on from my comment to the answer @bobby posted, here is the code I would use:

    function parseQuery(str)
        {
        if(typeof str != "string" || str.length == 0) return {};
        var s = str.split("&");
        var s_length = s.length;
        var bit, query = {}, first, second;
        for(var i = 0; i < s_length; i++)
            {
            bit = s[i].split("=");
            first = decodeURIComponent(bit[0]);
            if(first.length == 0) continue;
            second = decodeURIComponent(bit[1]);
            if(typeof query[first] == "undefined") query[first] = second;
            else if(query[first] instanceof Array) query[first].push(second);
            else query[first] = [query[first], second]; 
            }
        return query;
        }

This code takes in the querystring provided (as 'str') and returns an object. The string is split on all occurances of &, resulting in an array. the array is then travsersed and each item in it is split by "=". This results in sub arrays wherein the 0th element is the parameter and the 1st element is the value (or undefined if no = sign). These are mapped to object properties, so for example the string "hello=1&another=2&something" is turned into:

{
hello: "1",
another: "2",
something: undefined
}

In addition, this code notices repeating reoccurances such as "hello=1&hello=2" and converts the result into an array, eg:

{
hello: ["1", "2"]
}

You'll also notice it deals with cases in whih the = sign is not used. It also ignores if there is an equal sign straight after an & symbol.

A bit overkill for the original question, but a reusable solution if you ever need to work with querystrings in javascript :)

Answer 7

If you know that you will only have that one querystring variable you can simply do:

var dest = location.search.replace(/^.*?\=/, '');

Answer 8

The following function will parse the search string with a regular expression, cache the result and return the value of the requested variable:

window.getSearch = function(variable) {
  var parsedSearch;
  parsedSearch = window.parsedSearch || (function() {
    var match, re, ret;
    re = /\??(.*?)=([^\&]*)&?/gi;
    ret = {};
    while (match = re.exec(document.location.search)) {
      ret[match[1]] = match[2];
    }
    return window.parsedSearch = ret;
  })();
  return parsedSearch[variable];
};

You can either call it once without any parameters and work with the window.parsedSearch object, or call getSearch subsequently. I haven't fully tested this, the regular expression might still need some tweaking...

Answer 9

How about this?

function getQueryVar(varName){
    // Grab and unescape the query string - appending an '&' keeps the RegExp simple
    // for the sake of this example.
    var queryStr = unescape(window.location.search) + '&';

    // Dynamic replacement RegExp
    var regex = new RegExp('.*?[&\\?]' + varName + '=(.*?)&.*');

    // Apply RegExp to the query string
    var val = queryStr.replace(regex, "$1");

    // If the string is the same, we didn't find a match - return false
    return val == queryStr ? false : val;
}

..then just call it with:

alert('Var "dest" = ' + getQueryVar('dest'));

Cheers

Answer 10

I wanted a simple function that took a URL as an input and returned a map of the query params. If I were to improve this function, I would support the standard for array data in the URL, and or nested variables.

This should work back and for with the jQuery.param( qparams ) function.

function getQueryParams(url){
    var qparams = {},
        parts = (url||'').split('?'),
        qparts, qpart,
        i=0;

    if(parts.length <= 1 ){
        return qparams;
    }else{
        qparts = parts[1].split('&');
        for(i in qparts){

            qpart = qparts[i].split('=');
            qparams[decodeURIComponent(qpart[0])] = 
                           decodeURIComponent(qpart[1] || '');
        }
    }

    return qparams;
};

Answer 11

I wanted to pick up specific links within a DOM element on a page, send those users to a redirect page on a timer and then pass them onto the original clicked URL. This is how I did it using regular javascript incorporating one of the methods above.

Page with links: Head

  function replaceLinks() {   
var content = document.getElementById('mainContent');
            var nodes = content.getElementsByTagName('a');
        for (var i = 0; i < document.getElementsByTagName('a').length; i++) {
            {
                href = nodes[i].href;
                if (href.indexOf("thisurl.com") != -1) {

                    nodes[i].href="http://www.thisurl.com/redirect.aspx" + "?url=" + nodes[i];
                    nodes[i].target="_blank";

                }
            }
    }
}

Body

<body onload="replaceLinks()">

Redirect page Head

   function getQueryVariable(variable) {
        var query = window.location.search.substring(1);
        var vars = query.split('&');
        for (var i = 0; i < vars.length; i++) {
            var pair = vars[i].split('=');
            if (decodeURIComponent(pair[0]) == variable) {
                return decodeURIComponent(pair[1]);
            }
        }
        console.log('Query variable %s not found', variable);
    }
    function delayer(){
        window.location = getQueryVariable('url')
    }

Body

<body onload="setTimeout('delayer()', 1000)">