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what is the best way to extract variables with '=' from a string in javascript

I want to extract the variables names from a string like this: "foo=valor bar=second", and so on.
To return:
{
foo: "valor",
bar: "second",
...
}

You can use Regex Look Aheads to check for a variable name that is preceded by an = symbol
var str = "foo=valor bar=second";
var varRegex = /\w+(?=(\s)*(\=))/g;
var valueRegex = /(?<=(\=)[\s'"]*)\w+/g;
var varArr = str.match(varRegex);
var valueArr = str.match(valueRegex);
console.log(valueArr);
let obj = {};
for(let i in varArr) {
obj[varArr[i]] = valueArr[i];
}
console.log(obj);

var str = "foo=valor,bar=second";
var obj = {};
str.split(",").forEach(
function(item){
if(item){
var vars = item.split("=");
obj[vars[0]] = vars[1]
}
});
console.log(obj)

Different approach from the previous answer: You can split the string on spaces and then map the result array, splitting on the equal sign to create your object (left side is property, right side is value)
If you need it your specific format you can reduce it to convert the array into one big object with all the values
let a = "foo=valor bar=second"
console.log(a.split(' ').map((i,v) => { return JSON.parse(`{"${i.split('=')[0]}": "${i.split('=')[1]}"}`);}))
let b = a.split(' ').map((i,v) => { return JSON.parse(`{"${i.split('=')[0]}": "${i.split('=')[1]}"}`);})
console.log(b.reduce(function(acc, x) {
for (var key in x) acc[key] = x[key];
return acc;
}));

Not necessarily the quickest answer (in terms of speed of submission), but less regular expressions to maintain and less variables to store.
function toJSON(str) {
const regex = /(\w+)\=(\w+)\s*/g;
let result = {};
let match;
while (match = regex.exec(str)) {
result[match[1]] = match[2];
}
return result;
}
console.log(toJSON("foo=valor bar=second"));

How can I capture a hash to Object in functional JavaScript?

I'm writing a piece of code in JavaScript for modern browser. I'm not using lodash or underscore as we want to keep the library as small as possible.
For example,
If the url comes like this. http://something.com/#hash=value
And the app is configured to capture key hash then the result would be this. Nothing fancy. I was just wondering if there's a better way or simple way to do this.
{
'hash': 'value'
}
The code
var config = Object.assign({}, {
capturedHashParams: ['hash']
});
var hashValue = '#hash=value1'.substr(1);
var capturedHashParams = {};
if (config.capturedHashParams && Array.isArray(config.capturedHashParams)) {
var splitedHash = hashValue.split('=');
if (splitedHash.length > 0) {
var key = splitedHash[0] || '';
var value = splitedHash[1] || '';
if (key && value) {
config.capturedHashParams.forEach(function(hp) {
if (hp.toLowerCase().indexOf(key.toLowerCase()) > -1) {
capturedHashParams[key] = value;
}
});
}
}
}
console.log(capturedHashParams);
https://jsfiddle.net/c92p0rfm/2/

i think you are watching for something like this:
var output = [];
var hashString = window.location.hash;
var hashArray = hash.split('&');
for(var index = 0; index < hashArray.length; index++){
var text = hashArray[index];
var tempArray= text.split('=');
var object = {
id: tempArray[0],
value: tempArray[1]
};
output[index] = object;
}
now output looks like this:
[
{
id: "hash",
value: "value"
}
]

Your question is somewhat ambiguous. It appears that you want to extract key/value pairs from an url hash and return as a JavaScript object. I am bit uncertain about whether you want to extract all key/value pairs or only those provided in a config object. I am also a bit uncertain as to whether you want a solution within a strict functional programming paradigm, or just a plain solution with a small code footprint. I will assume the latter.
A straightforward approach to capture all key/value pairs:
var url = 'http://something.com/#hash=value&anotherHash=value';
//extract key=value pairs from url
var params = url.split('#').pop().split('&');
//assign to data object
for(var data = {}, i = 0, temp; i < params.length; i++){
// extract array [key, value]
temp = params[i].split('=');
// assign to data object
data[temp[0]] = temp[1];
}
console.log(data);
A more compact solution to do the same with .reduce():
var url = 'http://something.com/#hash=value&anotherHash=value';
var data = url
.split('#')
.pop()
.split('&')
.reduce(function(obj, keyval){
keyval = keyval.split('=');
obj[keyval[0]] = keyval[1];
return obj;
}, {});
console.log(data)
If you want to configure which keys to extract:
var url = 'http://something.com/#hash=value&anotherHash=value&notThisHash=value';
//config object
var keysToCapture = [
'hash',
'anotherHash'
];
var data = url
.split('#')
.pop()
.split('&')
.reduce(function(obj, keyval){
keyval = keyval.split('=');
if(keysToCapture.indexOf(keyval[0]) > -1){
obj[keyval[0]] = keyval[1];
}
return obj;
}, {});
console.log(data)
Which you could capture in a reusable function like this:
function extractParamsObject(url, keysToCapture){
return url
.split('#')
.pop() //hash/fragment: everything after the last #
.split('&')
.reduce(function(obj, keyval){
keyval = keyval.split('=');
if(keysToCapture.indexOf(keyval[0]) > -1){
obj[keyval[0]] = keyval[1];
}
return obj;
}, {});
}
console.log(extractParamsObject(
'http://something.com/#hash=value&anotherHash=value&notThisHash=value',
['hash', 'anotherHash']
));

Create deep object from string like "obj.obj1.obj2.data'

I'm starting with unit testing. I need to create some fake data to run the tests. So let's say inside a stubbed method I'm passing an obj as an argument and I do things with obj.obj1.obj2.data inside the function. Is there a way to set this fake object? So, given:
obj.obj1.obj2.data
It creates:
obj = {
obj1: {
obj2: {
data: 'whatever'}}}
So it would be at the end something like:
var obj = creator('obj.obj1.obj2.data', 20);

Assuming the string is only a set of objects (no arrays) this should be fairly straightforward. Just split the input string on . and then use a while loop to do the nesting.
function creator(str,val){
var tree = str.split('.');
var ret = {};
var cur = ret;
while(tree.length){
var name = tree.shift();
cur[name] = tree.length ? {} : val;
cur = cur[name];
}
return ret;
}
document.querySelector("#out").innerHTML = JSON.stringify(creator('obj.obj1.obj2.data',20));
<div id="out"></div>

Just in case anyone else in interested, I created a simple npm module with the function below (https://github.com/r01010010/zappy) check it out:
var objFrom = function(str, last_value){
var objs = str.split('.');
var r = {};
var last = r;
for(i=0; i < objs.length; i++) {
if(i !== objs.length - 1){
last = last[objs[i]] = {};
}else{
last[objs[i]] = last_value;
}
}
return r;
}
var obj = objFrom('obj1.obj2.data', 20);
console.log(obj.obj1.obj2.data);

Easy way to set javascript object multilevel property?

I am trying to create a javascript object like
var allUserExpiry={};
allUserExpiry[aData.userId][aData.courseId][aData.uscId] = aData;
But I am getting an error like allUserExpiry[aData.userId] undefined.
Is there a way, whereby I can set multi-level JS-Object keys? or is it important that I should go by doing allUserExpiry[aData.userId]={}, then allUserExpiry[aData.userId][aData.courseId]={} ?
Please let me know if there are any utility functions available for the same.

No, there is no way to set "multilevel keys". You need to initialize each object before trying to add properties to it.
var allUserExpiry = {};
allUserExpiry[aData.userId] = {}
allUserExpiry[aData.userId][aData.courseId] = {}
allUserExpiry[aData.userId][aData.courseId][aData.uscId] = aData;

Using Computed property names from ES6, it is possible to do:
var allUserExpiry = {
[aData.userId] = {
[aData.courseId]: {
[aData.uscId]: aData
}
}
};
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer#Computed_property_names

Simply use loadash,
let object = {};
let property = "a.b.c";
let value = 1;
_.set(object, property, value); // sets property based on path
let value = _.get(object, property, default); // gets property based on path

Or you can do it:
function setByPath(obj, path, value) {
var parts = path.split('.');
var o = obj;
if (parts.length > 1) {
for (var i = 0; i < parts.length - 1; i++) {
if (!o[parts[i]])
o[parts[i]] = {};
o = o[parts[i]];
}
}
o[parts[parts.length - 1]] = value;
}
And use:
setByPath(obj, 'path.path2.path', someValue);
This approach has many weak places, but for fun... :)

Why not just do this?
var allUserExpiry={};
allUserExpiry[aData.userId] = {aData.courseId: {aData.uscId: aData}};

I have a pretty hacky but short way of doing it in IE9+ as well as real browsers.
Given var path = 'aaa.bbb.ccc.ddd.eee'; where path is what your intending to make into an object and var result = {}; will will create the object {aaa: {bbb: {ccc: {ddd: {eee: {}}}}}
result = {}
path.split('.').reduce(function(prev, e) {
var newObj = {};
prev[e] = newObj;
return newObj;
}, result);
will store the object in result.
How it works:
split('.') converts the input into ['aaa', 'bbb', 'ccc', 'ddd', 'eee']
reduce(function (...) {...}, result) runs through the array created by split, and for each entry will pass along a returned value to the next one. In our case we pass the new object through after adding the new object to the old one. This creates a chain of objects. reduce returns the last object you return inside of it, so we have to defined result beforehand.
This relies on using references so it won't be immediately clear how it works if you're expecting your code to be maintained by anyone else and should probably be avoided to be honest, but it works at least.

You can also use the following to create the initial structure:
var x = function(obj, keys) {
if (!obj) return;
var i, t;
for (i = 0; i < keys.length; i++) {
if (!t) {
t = obj[keys[i]] = {};
} else {
t[keys[i]] = {};
t = t[keys[i]];
}
}
};
var a = {};
x(a, ['A', 'B', 'C', 'D', 'E', 'F']);

Another approach without strings or array as argument.
function fillObject() {
var o = arguments[0];
for(var i = 1; i < arguments.length-1; i++) {
if(!o.hasOwnProperty(arguments[i])) {
o[arguments[i]] = {};
}
if(i < arguments.length-2) {
o = o[arguments[i]];
}else {
o[arguments[i]] = arguments[i+1]
}
}
}
var myObj = {"foo":{}};
fillObject(myObj,"back","to","the","future",2);
console.log(JSON.stringify(myObj));
// {"foo":{},"back":{"to":{"the":{"future":2}}}}
But I wouldn't use it :-) It's just for fun.
Because I don't like too much intelligent algorithm. (If it was in this category)

Using lodash you can do this easily (node exists and empty check for that node)..
var lodash = require('lodash-contrib');
function invalidateRequest(obj, param) {
var valid = true;
param.forEach(function(val) {
if(!lodash.hasPath(obj, val)) {
valid = false;
} else {
if(lodash.getPath(obj, val) == null || lodash.getPath(obj, val) == undefined || lodash.getPath(obj, val) == '') {
valid = false;
}
}
});
return valid;
}
Usage:
leaveDetails = {
"startDay": 1414998000000,
"endDay": 1415084400000,
"test": { "test1" : 1234 }
};
var validate;
validate = invalidateRequest(leaveDetails, ['startDay', 'endDay', 'test.test1']);
it will return boolean.

Another solution using reduce function (thanks Brian K).
Here we created a get/set to general proposes. The first function return the value in any level. The key is splited considering the separator. the function return the value refered from last index in the key's array
The second function will set the new value considering the last index of the splited key
the code:
function getObjectMultiLevelValue(_array,key,separator){
key = key.split(separator || '.');
var _value = JSON.parse(JSON.stringify(_array));
for(var ki in key){
_value = _value[key[ki]];
}
return _value;
}
function setObjectMultiLevelValue(_array,key,value,forcemode,separator){
key.split(separator || '.').reduce(function(prev, currKey, currIndex,keysArr) {
var newObj = {};
if(prev[currKey] && !forcemode){
newObj = prev[currKey];
}
if(keysArr[keysArr.length-1] == currKey){
newObj = value;
prev[currKey] = newObj;
}
prev[currKey] = newObj;
return newObj;
}, _array);
return _array;
}
//testing the function
//creating an array
var _someArray = {a:'a',b:'b',c:{c1:'c1',c2:{c21:'nothing here...'}}};
//a multilevel key to test
var _key = 'a,a1,a21';
//any value
var _value = 'new foo in a21 key forcing replace old path';
//here the new value will be inserted even if the path exists (forcemode=true). Using comma separator
setObjectMultiLevelValue(_someArray,_key,_value,true,',');
console.log('_someArray:');
console.log(JSON.stringify(_someArray));
//inserting another value in another key... using default separator
_key = 'c.c2.c21';
_value = 'new foo in c21 key';
setObjectMultiLevelValue(_someArray,_key,_value);
console.log('_someArray:');
console.log(JSON.stringify(_someArray));
//recovering the saved value with different separators
_key = 'a,a1,a21';
console.log(getObjectMultiLevelValue(_someArray,_key,','));
_key = 'c.c2.c21';
console.log(getObjectMultiLevelValue(_someArray,_key));

Let assume our object is
const data = {
//some other data
userInfo: {},
};
First, define a new property of that object
data.userInfo.vehicle = {};
then simply
data.userInfo.vehicle.vehicleType = state.userInfo.vehicleType;

The $.param( ) inverse function in JavaScript / jQuery

Given the following form:
<form>
<input name="foo" value="bar">
<input name="hello" value="hello world">
</form>
I can use the $.param( .. ) construct to serialize the form:
$.param( $('form input') )
=> foo=bar&hello=hello+world
How can I deserialize the above String with JavaScript and get a hash back?
For example,
$.magicFunction("foo=bar&hello=hello+world")
=> {'foo' : 'bar', 'hello' : 'hello world'}
Reference: jQuery.param( obj ).

You should use jQuery BBQ's deparam function. It's well-tested and documented.

This is a slightly modified version of a function I wrote a while ago to do something similar.
var QueryStringToHash = function QueryStringToHash (query) {
var query_string = {};
var vars = query.split("&");
for (var i=0;i<vars.length;i++) {
var pair = vars[i].split("=");
pair[0] = decodeURIComponent(pair[0]);
pair[1] = decodeURIComponent(pair[1]);
// If first entry with this name
if (typeof query_string[pair[0]] === "undefined") {
query_string[pair[0]] = pair[1];
// If second entry with this name
} else if (typeof query_string[pair[0]] === "string") {
var arr = [ query_string[pair[0]], pair[1] ];
query_string[pair[0]] = arr;
// If third or later entry with this name
} else {
query_string[pair[0]].push(pair[1]);
}
}
return query_string;
};

How about this short functional approach?
function parseParams(str) {
return str.split('&').reduce(function (params, param) {
var paramSplit = param.split('=').map(function (value) {
return decodeURIComponent(value.replace(/\+/g, ' '));
});
params[paramSplit[0]] = paramSplit[1];
return params;
}, {});
}
Example:
parseParams("this=is&just=an&example") // Object {this: "is", just: "an", example: undefined}

My answer:
function(query){
var setValue = function(root, path, value){
if(path.length > 1){
var dir = path.shift();
if( typeof root[dir] == 'undefined' ){
root[dir] = path[0] == '' ? [] : {};
}
arguments.callee(root[dir], path, value);
}else{
if( root instanceof Array ){
root.push(value);
}else{
root[path] = value;
}
}
};
var nvp = query.split('&');
var data = {};
for( var i = 0 ; i < nvp.length ; i++ ){
var pair = nvp[i].split('=');
var name = decodeURIComponent(pair[0]);
var value = decodeURIComponent(pair[1]);
var path = name.match(/(^[^\[]+)(\[.*\]$)?/);
var first = path[1];
if(path[2]){
//case of 'array[level1]' || 'array[level1][level2]'
path = path[2].match(/(?=\[(.*)\]$)/)[1].split('][')
}else{
//case of 'name'
path = [];
}
path.unshift(first);
setValue(data, path, value);
}
return data;
}

I am using David Dorward's answer, and realized that it doesn't behave like PHP or Ruby on Rails how they parse the params:
1) a variable is only an array if it ends with [], such as ?choice[]=1&choice[]=12, not when it is ?a=1&a=2
2) when mulitple params exist with the same name, the later ones replaces the earlier ones, as on PHP servers (Ruby on Rails keep the first one and ignore the later ones), such as ?a=1&b=2&a=3
So modifying David's version, I have:
function QueryStringToHash(query) {
if (query == '') return null;
var hash = {};
var vars = query.split("&");
for (var i = 0; i < vars.length; i++) {
var pair = vars[i].split("=");
var k = decodeURIComponent(pair[0]);
var v = decodeURIComponent(pair[1]);
// If it is the first entry with this name
if (typeof hash[k] === "undefined") {
if (k.substr(k.length-2) != '[]') // not end with []. cannot use negative index as IE doesn't understand it
hash[k] = v;
else
hash[k.substr(0, k.length-2)] = [v];
// If subsequent entry with this name and not array
} else if (typeof hash[k] === "string") {
hash[k] = v; // replace it
// If subsequent entry with this name and is array
} else {
hash[k.substr(0, k.length-2)].push(v);
}
}
return hash;
};
which is tested fairly thoroughly.

I know this is an old thread, but maybe there is still some relevance in it?
Inspired by Jacky Li's good solution I tried a slight variation of my own with the objective to also be able to take care of arbitrary combinations of arrays and objects as input. I looked at how PHP would have done it and tried to get something "similar" going. Here is my code:
function getargs(str){
var ret={};
function build(urlnam,urlval,obj){ // extend the return object ...
var i,k,o=obj, x, rx=/\[([^\]]*)\]/g, idx=[urlnam.replace(rx,'')];
while (x=rx.exec(urlnam)) idx.push(x[1]);
while(true){
k=idx.shift();
if(k.trim()=='') {// key is empty: autoincremented index
if (o.constructor.name=='Array') k=o.length; // for Array
else if (o===obj ) {k=null} // for first level property name
else {k=-1; // for Object
for(i in o) if (+i>k) k=+i;
k++;
}
}
if(idx.length) {
// set up an array if the next key (idx[0]) appears to be
// numeric or empty, otherwise set up an object:
if (o[k]==null || typeof o[k]!='object') o[k]=isNaN(idx[0])?{}:[];
o=o[k]; // move on to the next level
}
else { // OK, time to store the urlval in its chosen place ...
// console.log('key',k,'val',urlval);
o[k]=urlval===""?null:urlval; break; // ... and leave the while loop.
}
}
return obj;
}
// ncnvt: is a flag that governs the conversion of
// numeric strings into numbers
var ncnvt=true,i,k,p,v,argarr=[],
ar=(str||window.location.search.substring(1)).split("&"),
l=ar.length;
for (i=0;i<l;i++) {if (ar[i]==="") continue;
p=ar[i].split("=");k=decodeURIComponent(p[0]);
v=p[1];v=(v!=null)?decodeURIComponent(v.replace(/\+/g,'%20')):'';
if (ncnvt && v.trim()>"" && !isNaN(v)) v-=0;
argarr.push([k,v]); // array: key-value-pairs of all arguments
}
for (i=0,l=argarr.length;i<l;i++) build(argarr[i][0],argarr[i][1],ret);
return ret;
}
If the function is called without the str-argument it will assume window.location.search.slice(1) as input.
Some examples:
['a=1&a=2', // 1
'x[y][0][z][]=1', // 2
'hello=[%22world%22]&world=hello', // 3
'a=1&a=2&&b&c=3&d=&=e&', // 4
'fld[2][]=2&fld[][]=3&fld[3][]=4&fld[]=bb&fld[]=cc', // 5
$.param({a:[[1,2],[3,4],{aa:'one',bb:'two'},[5,6]]}), // 6
'a[]=hi&a[]=2&a[3][]=7&a[3][]=99&a[]=13',// 7
'a[x]=hi&a[]=2&a[3][]=7&a[3][]=99&a[]=13'// 8
].map(function(v){return JSON.stringify(getargs(v));}).join('\n')
results in
{"a":2} // 1
{"x":{"y":[{"z":[1]}]}} // 2
{"hello":"[\"world\"]","world":"hello"} // 3
{"a":2,"b":null,"c":3,"d":null,"null":"e"} // 4 = { a: 2, b: null, c: 3, d: null, null: "e" }
{"fld":[null,null,[2],[3,4],"bb","cc"]} // 5
{"a":[[1,2],[3,4],{"aa":"one","bb":"two"},[5,6]]} // 6
{"a":["hi",2,null,[7,99],13]} // 7
{"a":{"0":2,"3":[7,99],"4":13,"x":"hi"}} // 8
Whereas Jacky Li's solution would produce the outer container for a as a plain object
{a:{"0":["1","2"],"1":["3","4"],"2":["5","6"]}} // 6: JackyLi's output
getargs() looks at the first given index for any level to determine whether this level will be an object (non-numeric index) or an array (numeric or empty), thus resulting in the output as shown in the listing bove (no. 6).
If the current object is an array then nulls get inserted wherever necessary to represent empty positions. Arrays are always consecutively numbered and 0-based).
Note, that in the example no. 8 the "autoincrement" for empty indices still works, even though we are dealing with an object now and not an array.
As far as I have tested it, my getargs() behaves pretty much identically to Chriss Roger's great jQuery $.deparam() plugin mentioned in the accepted answer. The main difference is that getargs runs without jQuery and that it does autoincrement in objects while $.deparam() will not do that:
JSON.stringify($.deparam('a[x]=hi&a[]=2&a[3][]=7&a[3][]=99&a[]=13').a);
results in
{"3":["7","99"],"x":"hi","undefined":"13"}
In $.deparam() the index [] is interpreted as an undefined instead of an autoincremented numerical index.

Here's how you could create a new jQuery function:
jQuery.unparam = function (value) {
var
// Object that holds names => values.
params = {},
// Get query string pieces (separated by &)
pieces = value.split('&'),
// Temporary variables used in loop.
pair, i, l;
// Loop through query string pieces and assign params.
for (i = 0, l = pieces.length; i < l; i++) {
pair = pieces[i].split('=', 2);
// Repeated parameters with the same name are overwritten. Parameters
// with no value get set to boolean true.
params[decodeURIComponent(pair[0])] = (pair.length == 2 ?
decodeURIComponent(pair[1].replace(/\+/g, ' ')) : true);
}
return params;
};

Thanks to him http://james.padolsey.com/javascript/parsing-urls-with-the-dom/
Pretty easy :D
function params_unserialize(p){
var ret = {},
seg = p.replace(/^\?/,'').split('&'),
len = seg.length, i = 0, s;
for (;i<len;i++) {
if (!seg[i]) { continue; }
s = seg[i].split('=');
ret[s[0]] = s[1];
}
return ret;}

This is really old question, but as i have coming - other people may coming to this post, and i want to a bit refresh this theme. Today no need to make custom solutions - there is URLSearchParams interface.
var paramsString = "q=URLUtils.searchParams&topic=api";
var searchParams = new URLSearchParams(paramsString);
//Iterate the search parameters.
for (let p of searchParams) {
console.log(p);
}
The only one limitation i know - this feature not supported in IE / Edge.

Here's my JavaScript implementation which I use in a server-side JScript ASP Classic page (demo):
// Transforms a query string in the form x[y][0][z][]=1 into {x:{y:[{z:[1]}]}}
function parseJQueryParams(p) {
var params = {};
var pairs = p.split('&');
for (var i=0; i<pairs.length; i++) {
var pair = pairs[i].split('=');
var indices = [];
var name = decodeURIComponent(pair[0]),
value = decodeURIComponent(pair[1]);
var name = name.replace(/\[([^\]]*)\]/g,
function(k, idx) { indices.push(idx); return ""; });
indices.unshift(name);
var o = params;
for (var j=0; j<indices.length-1; j++) {
var idx = indices[j];
var nextIdx = indices[j+1];
if (!o[idx]) {
if ((nextIdx == "") || (/^[0-9]+$/.test(nextIdx)))
o[idx] = [];
else
o[idx] = {};
}
o = o[idx];
}
idx = indices[indices.length-1];
if (idx == "") {
o.push(value);
}
else {
o[idx] = value;
}
}
return params;
}

I came up with this solution, which behaves like the .Net function HttpUtility.ParseQueryString.
In the result, the query string parameters are store in properties as lists of values, so that qsObj["param"] will be the same as calling GetValues("param") in .Net.
I hope you like it. JQuery not required.
var parseQueryString = function (querystring) {
var qsObj = new Object();
if (querystring) {
var parts = querystring.replace(/\?/, "").split("&");
var up = function (k, v) {
var a = qsObj[k];
if (typeof a == "undefined") {
qsObj[k] = [v];
}
else if (a instanceof Array) {
a.push(v);
}
};
for (var i in parts) {
var part = parts[i];
var kv = part.split('=');
if (kv.length == 1) {
var v = decodeURIComponent(kv[0] || "");
up(null, v);
}
else if (kv.length > 1) {
var k = decodeURIComponent(kv[0] || "");
var v = decodeURIComponent(kv[1] || "");
up(k, v);
}
}
}
return qsObj;
};
Here is how to use it:
var qsObj = parseQueryString("a=1&a=2&&b&c=3&d=&=e&");
To preview the result in the console juste type in:
JSON.stringify(qsObj)
Output:
"{"a":["1","2"],"null":["","b",""],"c":["3"],"d":[""],"":["e"]}"

There's a beautiful one-liner over at CSS-Tricks (original source from Nicholas Ortenzio):
function getQueryParameters(str) {
return (str || document.location.search).replace(/(^\?)/,'').split("&").map(function(n){return n = n.split("="),this[n[0]] = n[1],this}.bind({}))[0];
}
The really clever part is how it uses the anonymous function's this object, adding a key/value pair for each of the queries in the string. That said, there's some room for improvement. I've modified it a bit below, with the following changes:
Added handling of empty strings and non-string input.
Handled URI-encoded strings (%40->#, etc).
Removed the default use of document.location.search when the input was empty.
Changed the name, made it more readable, added comments.
function deparam(str) {
// Uses an empty 'this' to build up the results internally
function splitQuery(query) {
query = query.split('=').map(decodeURIComponent);
this[query[0]] = query[1];
return this;
}
// Catch bad input
if (!str || !(typeof str === 'string' || str instanceof String))
return {};
// Split the string, run splitQuery on each piece, and return 'this'
var queries = str.replace(/(^\?)/,'').split('&');
return queries.map(splitQuery.bind({}))[0];
}

use this :
// convert query string to json object
var queryString = "cat=3&sort=1&page=1";
queryString
.split("&")
.forEach((item) => {
const prop = item.split("=");
filter[prop[0]] = prop[1];
});
console.log(queryString);

This is my version in Coffeescript.
Also works for url like
http://localhost:4567/index.html?hello=[%22world%22]&world=hello#/home
getQueryString: (url)->
return null if typeof url isnt 'string' or url.indexOf("http") is -1
split = url.split "?"
return null if split.length < 2
path = split[1]
hash_pos = path.indexOf "#"
path = path[0...hash_pos] if hash_pos isnt -1
data = path.split "&"
ret = {}
for d in data
[name, val] = d.split "="
name = decodeURIComponent name
val = decodeURIComponent val
try
ret[name] = JSON.parse val
catch error
ret[name] = val
return ret

Here's a simple & compact one if you only want to quickly get the parameters from a GET request:
function httpGet() {
var a={},b,i,q=location.search.replace(/^\?/,"").split(/\&/);
for(i in q) if(q[i]) {b=q[i].split("=");if(b[0]) a[b[0]]=
decodeURIComponent(b[1]).replace(/\+/g," ");} return a;
}
It converts
something?aa=1&bb=2&cc=3
into an object like
{aa:1,bb:2,cc:3}

Creates a serialized representation of an array or object (can be used as URL query string for AJAX requests).
<button id='param'>GET</button>
<div id="show"></div>
<script>
$('#param').click(function () {
var personObj = new Object();
personObj.firstname = "vishal"
personObj.lastname = "pambhar";
document.getElementById('show').innerHTML=$.param(`personObj`));
});
</script>
output:firstname=vishal&lastname=pambhar

answers could use a bit of jQuery elegance:
(function($) {
var re = /([^&=]+)=?([^&]*)/g;
var decodeRE = /\+/g; // Regex for replacing addition symbol with a space
var decode = function (str) {return decodeURIComponent( str.replace(decodeRE, " ") );};
$.parseParams = function(query) {
var params = {}, e;
while ( e = re.exec(query) ) {
var k = decode( e[1] ), v = decode( e[2] );
if (k.substring(k.length - 2) === '[]') {
k = k.substring(0, k.length - 2);
(params[k] || (params[k] = [])).push(v);
}
else params[k] = v;
}
return params;
};
})(jQuery);
fork at https://gist.github.com/956897

You can use the function .serializeArray() (Link) of jQuery itself. This function returns an array of key-value pair. Result example:
[
{ name: "id", value: "1" },
{ name: "version", value: "100" }
]