Query-string encoding of a JavaScript object

Question

Is there a fast and simple way to encode a JavaScript object into a string that I can pass via a GET request?

No jQuery, no other frameworks—just plain JavaScript :)

Answer 1

Like this:

serialize = function(obj) {
  var str = [];
  for (var p in obj)
    if (obj.hasOwnProperty(p)) {
      str.push(encodeURIComponent(p) + "=" + encodeURIComponent(obj[p]));
    }
  return str.join("&");
}

console.log(serialize({
  foo: "hi there",
  bar: "100%"
}));
// foo=hi%20there&bar=100%25

This one also converts recursive objects (using PHP "array" notation for the query string):

serialize = function(obj, prefix) {
  var str = [],
    p;
  for (p in obj) {
    if (obj.hasOwnProperty(p)) {
      var k = prefix ? prefix + "[" + p + "]" : p,
        v = obj[p];
      str.push((v !== null && typeof v === "object") ?
        serialize(v, k) :
        encodeURIComponent(k) + "=" + encodeURIComponent(v));
    }
  }
  return str.join("&");
}

console.log(serialize({
  foo: "hi there",
  bar: {
    blah: 123,
    quux: [1, 2, 3]
  }
}));
// foo=hi%20there&bar%5Bblah%5D=123&bar%5Bquux%5D%5B0%5D=1&bar%5Bquux%5D%5B1%5D=2&bar%5Bquux%5D%5B2%5D=3

Answer 2

Just use URLSearchParams This works in all current browsers

new URLSearchParams(object).toString()

Answer 3

jQuery has a function for this, jQuery.param(). If you're already using it, you can use this:

Example:

var params = { width:1680, height:1050 };
var str = jQuery.param( params );

str now contains width=1680&height=1050.

Answer 4

I suggest using the URLSearchParams interface:

const searchParams = new URLSearchParams();
const params = {foo: "hi there", bar: "100%" };
Object.keys(params).forEach(key => searchParams.append(key, params[key]));
console.log(searchParams.toString())

Or by passing the search object into the constructor like this:

const params = {foo: "hi there", bar: "100%" };
const queryString = new URLSearchParams(params).toString();
console.log(queryString);

Answer 5

Use:

Object.keys(obj).reduce(function(a,k){a.push(k+'='+encodeURIComponent(obj[k]));return a},[]).join('&')

I like this one-liner, but I bet it would be a more popular answer if it matched the accepted answer semantically:

function serialize( obj ) {
    let str = '?' + Object.keys(obj).reduce(function(a, k){
        a.push(k + '=' + encodeURIComponent(obj[k]));
        return a;
    }, []).join('&');
    return str;
}

Answer 6

Here's a one liner in ES6:

Object.keys(obj).map(k => `${encodeURIComponent(k)}=${encodeURIComponent(obj[k])}`).join('&');

Answer 7

With Node.js v6.6.3

const querystring = require('querystring')

const obj = {
  foo: 'bar',
  baz: 'tor'
}

let result = querystring.stringify(obj)
// foo=bar&baz=tor

Reference: Query string

Answer 8

Ruby on Rails and PHP style query builder

This method converts a JavaScript object into a URI query string. It also handles nested arrays and objects (in Ruby on Rails and PHP syntax):

function serializeQuery(params, prefix) {
  const query = Object.keys(params).map((key) => {
    const value  = params[key];

    if (params.constructor === Array)
      key = `${prefix}[]`;
    else if (params.constructor === Object)
      key = (prefix ? `${prefix}[${key}]` : key);

    if (typeof value === 'object')
      return serializeQuery(value, key);
    else
      return `${key}=${encodeURIComponent(value)}`;
  });

  return [].concat.apply([], query).join('&');
}

---

Example Usage:

let params = {
  a: 100,
  b: 'has spaces',
  c: [1, 2, 3],
  d: { x: 9, y: 8}
}

serializeQuery(params)
// returns 'a=100&b=has%20spaces&c[]=1&c[]=2&c[]=3&d[x]=9&d[y]=8

Answer 9

A small amendment to the accepted solution by user187291:

serialize = function(obj) {
   var str = [];
   for(var p in obj){
       if (obj.hasOwnProperty(p)) {
           str.push(encodeURIComponent(p) + "=" + encodeURIComponent(obj[p]));
       }
   }
   return str.join("&");
}

Checking for hasOwnProperty on the object makes JSLint and JSHint happy, and it prevents accidentally serializing methods of the object or other stuff if the object is anything but a simple dictionary. See the paragraph on for statements on Code Conventions for the JavaScript Programming Language.

Answer 10

Here is a one-liner:

const encoded = Object.entries(obj).map(([k, v]) => `${k}=${encodeURIComponent(v)}`).join("&");

Answer 11

If you need to send arbitrary objects, then GET is a bad idea since there are limits to the lengths of URLs that user agents and web servers will accepts. My suggestion would be to build up an array of name-value pairs to send and then build up a query string:

function QueryStringBuilder() {
    var nameValues = [];

    this.add = function(name, value) {
        nameValues.push( {name: name, value: value} );
    };

    this.toQueryString = function() {
        var segments = [], nameValue;
        for (var i = 0, len = nameValues.length; i < len; i++) {
            nameValue = nameValues[i];
            segments[i] = encodeURIComponent(nameValue.name) + "=" + encodeURIComponent(nameValue.value);
        }
        return segments.join("&");
    };
}

var qsb = new QueryStringBuilder();
qsb.add("veg", "cabbage");
qsb.add("vegCount", "5");

alert( qsb.toQueryString() );

Answer 12

Use:

const toQueryString = obj => "?".concat(Object.keys(obj).map(e => `${encodeURIComponent(e)}=${encodeURIComponent(obj[e])}`).join("&"));

const data = {
  offset: 5,
  limit: 10
};

toQueryString(data); // => ?offset=5&limit=10

Or use a predefined feature

const data = {
  offset: 5,
  limit: 10
};

new URLSearchParams(data).toString(); // => ?offset=5&limit=10

Note

Both the above methods will set the value as null if not present. If you want not to set the query parameter if value is null then use:

const toQueryString = obj => "?".concat(Object.keys(obj).map(e => obj[e] ? `${encodeURIComponent(e)}=${encodeURIComponent(obj[e])}` : null).filter(e => !!e).join("&"));


const data = {
  offset: null,
  limit: 10
};

toQueryString(data); // => "?limit=10" else with above methods "?offset=null&limit=10"

You can freely use any method.

Answer 13

A little bit look better

objectToQueryString(obj, prefix) {
    return Object.keys(obj).map(objKey => {
        if (obj.hasOwnProperty(objKey)) {
            const key = prefix ? `${prefix}[${objKey}]` : objKey;
            const value = obj[objKey];

            return typeof value === "object" ?
                this.objectToQueryString(value, key) :
                `${encodeURIComponent(key)}=${encodeURIComponent(value)}`;
        }

        return null;
    }).join("&");
}

Answer 14

This one skips null/undefined values

export function urlEncodeQueryParams(data) {
    const params = Object.keys(data).map(key => data[key] ? `${encodeURIComponent(key)}=${encodeURIComponent(data[key])}` : '');
    return params.filter(value => !!value).join('&');
}

Answer 15

Here's the CoffeeScript version of the accepted answer.

serialize = (obj, prefix) ->
  str = []
  for p, v of obj
    k = if prefix then prefix + "[" + p + "]" else p
    if typeof v == "object"
      str.push(serialize(v, k))
    else
      str.push(encodeURIComponent(k) + "=" + encodeURIComponent(v))

  str.join("&")

Answer 16

Here's a concise & recursive version with Object.entries. It handles arbitrarily nested arrays, but not nested objects. It also removes empty elements:

const format = (k,v) => v !== null ? `${k}=${encodeURIComponent(v)}` : ''

const to_qs = (obj) => {
    return [].concat(...Object.entries(obj)
                       .map(([k,v]) => Array.isArray(v) 
                          ? v.map(arr => to_qs({[k]:arr})) 
                          : format(k,v)))
           .filter(x => x)
           .join('&');
}

E.g.:

let json = { 
    a: [1, 2, 3],
    b: [],              // omit b
    c: 1,
    d: "test&encoding", // uriencode
    e: [[4,5],[6,7]],   // flatten this
    f: null,            // omit nulls
    g: 0
};

let qs = to_qs(json)

=> "a=1&a=2&a=3&c=1&d=test%26encoding&e=4&e=5&e=6&e=7&g=0"

Answer 17

There another popular library, qs. You can add it by:

yarn add qs

And then use it like this:

import qs from 'qs'

const array = { a: { b: 'c' } }
const stringified = qs.stringify(array, { encode: false })

console.log(stringified) //-- outputs a[b]=c

Answer 18

I made a comparison of JSON stringifiers and the results are as follows:

JSON:    {"_id":"5973782bdb9a930533b05cb2","isActive":true,"balance":"$1,446.35","age":32,"name":"Logan Keller","email":"[email protected]","phone":"+1 (952) 533-2258","friends":[{"id":0,"name":"Colon Salazar"},{"id":1,"name":"French Mcneil"},{"id":2,"name":"Carol Martin"}],"favoriteFruit":"banana"}
Rison:   (_id:'5973782bdb9a930533b05cb2',age:32,balance:'$1,446.35',email:'[email protected]',favoriteFruit:banana,friends:!((id:0,name:'Colon Salazar'),(id:1,name:'French Mcneil'),(id:2,name:'Carol Martin')),isActive:!t,name:'Logan Keller',phone:'+1 (952) 533-2258')
O-Rison: _id:'5973782bdb9a930533b05cb2',age:32,balance:'$1,446.35',email:'[email protected]',favoriteFruit:banana,friends:!((id:0,name:'Colon Salazar'),(id:1,name:'French Mcneil'),(id:2,name:'Carol Martin')),isActive:!t,name:'Logan Keller',phone:'+1 (952) 533-2258'
JSURL:   ~(_id~'5973782bdb9a930533b05cb2~isActive~true~balance~'!1*2c446.35~age~32~name~'Logan*20Keller~email~'logankeller*40artiq.com~phone~'*2b1*20*28952*29*20533-2258~friends~(~(id~0~name~'Colon*20Salazar)~(id~1~name~'French*20Mcneil)~(id~2~name~'Carol*20Martin))~favoriteFruit~'banana)
QS:      _id=5973782bdb9a930533b05cb2&isActive=true&balance=$1,446.35&age=32&name=Logan Keller&[email protected]&phone=+1 (952) 533-2258&friends[0][id]=0&friends[0][name]=Colon Salazar&friends[1][id]=1&friends[1][name]=French Mcneil&friends[2][id]=2&friends[2][name]=Carol Martin&favoriteFruit=banana
URLON:   $_id=5973782bdb9a930533b05cb2&isActive:true&balance=$1,446.35&age:32&name=Logan%20Keller&[email protected]&phone=+1%20(952)%20533-2258&friends@$id:0&name=Colon%20Salazar;&$id:1&name=French%20Mcneil;&$id:2&name=Carol%20Martin;;&favoriteFruit=banana
QS-JSON: isActive=true&balance=%241%2C446.35&age=32&name=Logan+Keller&email=logankeller%40artiq.com&phone=%2B1+(952)+533-2258&friends(0).id=0&friends(0).name=Colon+Salazar&friends(1).id=1&friends(1).name=French+Mcneil&friends(2).id=2&friends(2).name=Carol+Martin&favoriteFruit=banana

The shortest among them is URL Object Notation.

Answer 19

I have a simpler solution that does not use any third-party library and is already apt to be used in any browser that has "Object.keys" (aka all modern browsers + Edge + Internet Explorer):

In ES5:

function(a){
    if( typeof(a) !== 'object' )
        return '';
    return `?${Object.keys(a).map(k=>`${k}=${a[k]}`).join('&')}`;
}

In ES3:

function(a){
    if( typeof(a) !== 'object' )
        return '';
    return '?' + Object.keys(a).map(function(k){ return k + '=' + a[k] }).join('&');
}

Answer 20

ES6 solution for query string encoding of a JavaScript object

const params = {
  a: 1,
  b: 'query stringify',
  c: null,
  d: undefined,
  f: '',
  g: { foo: 1, bar: 2 },
  h: ['Winterfell', 'Westeros', 'Braavos'],
  i: { first: { second: { third: 3 }}}
}

static toQueryString(params = {}, prefix) {
  const query = Object.keys(params).map((k) => {
    let key = k;
    const value = params[key];

    if (!value && (value === null || value === undefined || isNaN(value))) {
      value = '';
    }

    switch (params.constructor) {
      case Array:
        key = `${prefix}[]`;
        break;
      case Object:
        key = (prefix ? `${prefix}[${key}]` : key);
        break;
    }

    if (typeof value === 'object') {
      return this.toQueryString(value, key); // for nested objects
    }

    return `${key}=${encodeURIComponent(value)}`;
  });

  return query.join('&');
}

toQueryString(params)

"a=1&b=query%20stringify&c=&d=&f=&g[foo]=1&g[bar]=2&h[]=Winterfell&h[]=Westeros&h[]=Braavos&i[first][second][third]=3"

Answer 21

A single line to convert an object into a query string in case somebody needs it again:

let Objs = { a: 'obejct-a', b: 'object-b' }

Object.keys(objs).map(key => key + '=' + objs[key]).join('&')

// The result will be a=object-a&b=object-b

Answer 22

This is an addition for the accepted solution. This works with objects and array of objects:

parseJsonAsQueryString = function (obj, prefix, objName) {
    var str = [];
    for (var p in obj) {
        if (obj.hasOwnProperty(p)) {
            var v = obj[p];
            if (typeof v == "object") {
                var k = (objName ? objName + '.' : '') + (prefix ? prefix + "[" + p + "]" : p);
                str.push(parseJsonAsQueryString(v, k));
            } else {
                var k = (objName ? objName + '.' : '') + (prefix ? prefix + '.' + p : p);
                str.push(encodeURIComponent(k) + "=" + encodeURIComponent(v));
                //str.push(k + "=" + v);
            }
        }
    }
    return str.join("&");
}

Also I have added objName if you're using object parameters, like in ASP.NET MVC action methods.

Answer 23

In ES7, you can write this in one line:

const serialize = (obj) => (Object.entries(obj).map(i => [i[0], encodeURIComponent(i[1])].join('=')).join('&'))

Answer 24

If you want to convert a nested object recursively and the object may or may not contain arrays (and the arrays may contain objects or arrays, etc), then the solution gets a little more complex. This is my attempt.

I've also added some options to choose if you want to record for each object member at what depth in the main object it sits, and to choose if you want to add a label to the members that come from converted arrays.

Ideally you should test if the thing parameter really receives an object or array.

function thingToString(thing,maxDepth,recordLevel,markArrays){
    //thing: object or array to be recursively serialized
    //maxDepth (int or false):
    // (int) how deep to go with converting objects/arrays within objs/arrays
    // (false) no limit to recursive objects/arrays within objects/arrays
    //recordLevel (boolean):
    //  true - insert "(level 1)" before transcript of members at level one (etc)
    //  false - just 
    //markArrays (boolean):
    //  insert text to indicate any members that came from arrays
    var result = "";
    if (maxDepth !== false && typeof maxDepth != 'number') {maxDepth = 3;}
    var runningDepth = 0;//Keeps track how deep we're into recursion

    //First prepare the function, so that it can call itself recursively
    function serializeAnything(thing){
        //Set path-finder values
        runningDepth += 1;
        if(recordLevel){result += "(level " + runningDepth + ")";}

        //First convert any arrays to object so they can be processed
        if (thing instanceof Array){
            var realObj = {};var key;
            if (markArrays) {realObj['type'] = "converted array";}
            for (var i = 0;i < thing.length;i++){
                if (markArrays) {key = "a" + i;} else {key = i;}
                realObj[key] = thing[i];
            }
            thing = realObj;
            console.log('converted one array to ' + typeof realObj);
            console.log(thing);
        }

        //Then deal with it
        for (var member in thing){
            if (typeof thing[member] == 'object' && runningDepth < maxDepth){
                serializeAnything(thing[member]);
                //When a sub-object/array is serialized, it will add one to
                //running depth. But when we continue to this object/array's
                //next sibling, the level must go back up by one
                runningDepth -= 1;
            } else if (maxDepth !== false && runningDepth >= maxDepth) {
                console.log('Reached bottom');
            } else 
            if (
                typeof thing[member] == "string" || 
                typeof thing[member] == 'boolean' ||
                typeof thing[member] == 'number'
            ){
                result += "(" + member + ": " + thing[member] + ") ";
            }  else {
                result += "(" + member + ": [" + typeof thing[member] + " not supported]) ";
            }
        }
    }
    //Actually kick off the serialization
    serializeAnything(thing);

    return result;

}

Answer 25

This is a solution that will work for .NET backends out of the box. I have taken the primary answer of this thread and updated it to fit our .NET needs.

function objectToQuerystring(params) {
var result = '';

    function convertJsonToQueryString(data, progress, name) {
        name = name || '';
        progress = progress || '';
        if (typeof data === 'object') {
            Object.keys(data).forEach(function (key) {
                var value = data[key];
                if (name == '') {
                    convertJsonToQueryString(value, progress, key);
                } else {
                    if (isNaN(parseInt(key))) {
                        convertJsonToQueryString(value, progress, name + '.' + key);
                    } else {
                        convertJsonToQueryString(value, progress, name + '[' + key+ ']');
                    }
                }
            })
        } else {
            result = result ? result.concat('&') : result.concat('?');
            result = result.concat(`${name}=${data}`);
        }
    }

    convertJsonToQueryString(params);
    return result;
}

Answer 26

I've written a package just for that: object-query-string :)

It supports nested objects, arrays, custom encoding functions, etc. It is lightweight and jQuery-free.

// TypeScript
import { queryString } from 'object-query-string';

// Node.js
const { queryString } = require("object-query-string");

const query = queryString({
    filter: {
        brands: ["Audi"],
        models: ["A4", "A6", "A8"],
        accidentFree: true
    },
    sort: 'mileage'
});

returns

filter[brands][]=Audi&filter[models][]=A4&filter[models][]=A6&filter[models][]=A8&filter[accidentFree]=true&sort=milage

Answer 27

After going through some top answers here, I have wrote another implementation that tackles some edge cases as well

function serialize(params, prefix) {                
    return Object.entries(params).reduce((acc, [key, value]) => {
        // remove whitespace from both sides of the key before encoding
        key = encodeURIComponent(key.trim());

        if (params.constructor === Array ) {
          key = `${prefix}[]`;
        } else if (params.constructor === Object) {
          key = (prefix ? `${prefix}[${key}]` : key);
        }

        /**
         *  - undefined and NaN values will be skipped automatically
         *  - value will be empty string for functions and null
         *  - nested arrays will be flattened
         */
        if (value === null || typeof value === 'function') {
            acc.push(`${key}=`);
        } else if (typeof value === 'object') {
            acc = acc.concat(serialize(value, key));
        } else if(['number', 'boolean', 'string'].includes(typeof value) && value === value) { // self-check to avoid NaN
            acc.push(`${key}=${encodeURIComponent(value)}`);
        }

        return acc;
    }, []);
}

function objectToQueryString(queryParameters) {
    return queryParameters ? serialize(queryParameters).join('&'): '';
}

let x = objectToQueryString({
    foo: 'hello world',
    bar: {
      blah: 123,
      list: [1, 2, 3],
        'nested array': [[4,5],[6,7]] // will be flattened
    },
    page: 1,
    limit: undefined, // field will be ignored
    check: false,
    max: NaN, // field will be ignored
    prop: null,
    ' key value': 'with spaces' // space in key will be trimmed out
});
  
console.log(x); // foo=hello%20world&bar[blah]=123&bar[list][]=1&bar[list][]=2&bar[list][]=3&bar[nested%20array][][]=4&bar[nested%20array][][]=5&bar[nested%20array][][]=6&bar[nested%20array][][]=7&page=1&check=false&prop=&key%20value=with%20spaces

Answer 28

The previous answers do not work if you have a lot of nested objects.

Instead you can pick the function parameter from jquery-param/jquery-param.js. It worked very well for me!

    var param = function (a) {
    var s = [], rbracket = /\[\]$/,
        isArray = function (obj) {
            return Object.prototype.toString.call(obj) === '[object Array]';
        }, add = function (k, v) {
            v = typeof v === 'function' ? v() : v === null ? '' : v === undefined ? '' : v;
            s[s.length] = encodeURIComponent(k) + '=' + encodeURIComponent(v);
        }, buildParams = function (prefix, obj) {
            var i, len, key;

            if (prefix) {
                if (isArray(obj)) {
                    for (i = 0, len = obj.length; i < len; i++) {
                        if (rbracket.test(prefix)) {
                            add(prefix, obj[i]);
                        } else {
                            buildParams(prefix + '[' + (typeof obj[i] === 'object' ? i : '') + ']', obj[i]);
                        }
                    }
                } else if (obj && String(obj) === '[object Object]') {
                    for (key in obj) {
                        buildParams(prefix + '[' + key + ']', obj[key]);
                    }
                } else {
                    add(prefix, obj);
                }
            } else if (isArray(obj)) {
                for (i = 0, len = obj.length; i < len; i++) {
                    add(obj[i].name, obj[i].value);
                }
            } else {
                for (key in obj) {
                    buildParams(key, obj[key]);
                }
            }
            return s;
        };

    return buildParams('', a).join('&').replace(/%20/g, '+');
};

Answer 29

ok, it's a older post but i'm facing this problem and i have found my personal solution.. maybe can help someone else..

     function objToQueryString(obj){
        var k = Object.keys(obj);
        var s = "";
        for(var i=0;i<k.length;i++) {
            s += k[i] + "=" + encodeURIComponent(obj[k[i]]);
            if (i != k.length -1) s += "&";
        }
        return s;
     };

Answer 30

URLSearchParams looks good, but it didn't work for nested objects.

Try to use

encodeURIComponent(JSON.stringify(object))