[javascript] Convert JS Object to form data

How can I can convert my JS Object to FormData?

The reason why I want to do this is, I have an object that I constructed out of the ~100 form field values.

var item = {
   description: 'Some Item',
   price : '0.00',
   srate : '0.00',
   color : 'red',
   ...
   ...
}

Now I am asked to add the upload file functionality to my form which, of-course is impossible via JSON and so I am planning on moving to FormData. So is there any way that I can convert my JS object to FormData?

Recursively

const toFormData = (f => f(f))(h => f => f(x => h(h)(f)(x)))(f => fd => pk => d => {_x000D_
  if (d instanceof Object) {_x000D_
    Object.keys(d).forEach(k => {_x000D_
      const v = d[k]_x000D_
      if (pk) k = `${pk}[${k}]`_x000D_
      if (v instanceof Object && !(v instanceof Date) && !(v instanceof File)) {_x000D_
        return f(fd)(k)(v)_x000D_
      } else {_x000D_
        fd.append(k, v)_x000D_
      }_x000D_
    })_x000D_
  }_x000D_
  return fd_x000D_
})(new FormData())()_x000D_
_x000D_
let data = {_x000D_
  name: 'John',_x000D_
  age: 30,_x000D_
  colors: ['red', 'green', 'blue'],_x000D_
  children: [_x000D_
    { name: 'Max', age: 3 },_x000D_
    { name: 'Madonna', age: 10 }_x000D_
  ]_x000D_
}_x000D_
console.log('data', data)_x000D_
document.getElementById("data").insertAdjacentHTML('beforeend', JSON.stringify(data))_x000D_
_x000D_
let formData = toFormData(data)_x000D_
_x000D_
for (let key of formData.keys()) {_x000D_
  console.log(key, formData.getAll(key).join(','))_x000D_
  document.getElementById("item").insertAdjacentHTML('beforeend', `<li>${key} = ${formData.getAll(key).join(',')}</li>`)_x000D_
}

<p id="data"></p>_x000D_
<ul id="item"></ul>

In my case my object also had property which was array of files. Since they are binary they should be dealt differently - index doesn't need to be part of the key. So i modified @Vladimir Novopashin's and @developer033's answer:

export function convertToFormData(data, formData, parentKey) {
  if(data === null || data === undefined) return null;

  formData = formData || new FormData();

  if (typeof data === 'object' && !(data instanceof Date) && !(data instanceof File)) {
    Object.keys(data).forEach(key => 
      convertToFormData(data[key], formData, (!parentKey ? key : (data[key] instanceof File ? parentKey : `${parentKey}[${key}]`)))
    );
  } else {
    formData.append(parentKey, data);
  }

  return formData;
}

I reference this from Gudradain's answer. I edit it a little in Typescript format.

class UtilityService {
    private appendFormData(formData, data, rootName) {

        let root = rootName || '';
        if (data instanceof File) {
            formData.append(root, data);
        } else if (Array.isArray(data)) {
            for (var i = 0; i < data.length; i++) {
                this.appendFormData(formData, data[i], root + '[' + i + ']');
            }
        } else if (typeof data === 'object' && data) {
            for (var key in data) {
                if (data.hasOwnProperty(key)) {
                    if (root === '') {
                        this.appendFormData(formData, data[key], key);
                    } else {
                        this.appendFormData(formData, data[key], root + '.' + key);
                    }
                }
            }
        } else {
            if (data !== null && typeof data !== 'undefined') {
                formData.append(root, data);
            }
        }
    }

    getFormDataFromObj(data) {
        var formData = new FormData();

        this.appendFormData(formData, data, '');

        return formData;
    }
}

export let UtilityMan = new UtilityService();

This method convert a JS object to a FormData :

function convertToFormData(params) {_x000D_
    return Object.entries(params)_x000D_
        .reduce((acc, [key, value]) => {_x000D_
            if (Array.isArray(value)) {_x000D_
                value.forEach((v, k) => acc.append(`${key}[${k}]`, value));_x000D_
            } else if (typeof value === 'object' && !(value instanceof File) && !(value instanceof Date)) {_x000D_
                Object.entries(value).forEach((v, k) => acc.append(`${key}[${k}]`, value));_x000D_
            } else {_x000D_
                acc.append(key, value);_x000D_
            }_x000D_
_x000D_
            return acc;_x000D_
        }, new FormData());_x000D_
}

• Handles nested objects and arrays
• Handles files
• Type support
• Tested in Chrome

const buildFormData = (formData: FormData, data: FormVal, parentKey?: string) => {
    if (isArray(data)) {
        data.forEach((el) => {
            buildFormData(formData, el, parentKey)
        })

    } else if (typeof data === "object" && !(data instanceof File)) {
        Object.keys(data).forEach((key) => {
            buildFormData(formData, (data as FormDataNest)[key], parentKey ? `${parentKey}.${key}` : key)
        })

    } else {
        if (isNil(data)) {
            return
        }

        let value = typeof data === "boolean" || typeof data === "number" ? data.toString() : data
        formData.append(parentKey as string, value)
    }
}

export const getFormData = (data: Record<string, FormDataNest>) => {
    const formData = new FormData()

    buildFormData(formData, data)

    return formData
}

Examples and Tests

const data = {
    filePhotos: imageArray,
}

yourAjaxCall({
   ...,
   data: getFormData(data)
})

Screenshot from Chrome dev tools - Network - Headers:

const data = {
    nested: {
        a: 1,
        b: ["hello", "world"],
        c: {
            d: 2,
            e: ["hello", "world"],
        }
    }
}

yourAjaxCall({
   ...,
   data: getFormData(data)
})

Here is a short and sweet solution using Object.entries() that will take care of even your nested objects.

// If this is the object you want to convert to FormData...
const item = {
    description: 'First item',
    price: 13,
    photo: File
};

const formData = new FormData();

Object.entries(item).forEach(([key, value]) => {
    formData.append(key, value);
});

// At this point, you can then pass formData to your handler method

Read more about Object.entries() over here - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries

You can simply install qs:

npm i qs

Simply import:

import qs from 'qs'

Pass object to qs.stringify():

var item = {
   description: 'Some Item',
   price : '0.00',
   srate : '0.00',
   color : 'red',
   ...
   ...
}

qs.stringify(item)

This function adds all data from object to FormData

ES6 version from @developer033:

function buildFormData(formData, data, parentKey) {
  if (data && typeof data === 'object' && !(data instanceof Date) && !(data instanceof File)) {
    Object.keys(data).forEach(key => {
      buildFormData(formData, data[key], parentKey ? `${parentKey}[${key}]` : key);
    });
  } else {
    const value = data == null ? '' : data;

    formData.append(parentKey, value);
  }
}

function jsonToFormData(data) {
  const formData = new FormData();
  
  buildFormData(formData, data);
  
  return formData;
}

const my_data = {
  num: 1,
  falseBool: false,
  trueBool: true,
  empty: '',
  und: undefined,
  nullable: null,
  date: new Date(),
  name: 'str',
  another_object: {
    name: 'my_name',
    value: 'whatever'
  },
  array: [
    {
      key1: {
        name: 'key1'
      }
    }
  ]
};

jsonToFormData(my_data)

jQuery version:

function appendFormdata(FormData, data, name){
    name = name || '';
    if (typeof data === 'object'){
        $.each(data, function(index, value){
            if (name == ''){
                appendFormdata(FormData, value, index);
            } else {
                appendFormdata(FormData, value, name + '['+index+']');
            }
        })
    } else {
        FormData.append(name, data);
    }
}


var formData = new FormData(),
    your_object = {
        name: 'test object',
        another_object: {
            name: 'and other objects',
            value: 'whatever'
        }
    };
appendFormdata(formData, your_object); 

I might be a little late to the party but this is what I've created to convert a singular object to FormData.

function formData(formData, filesIgnore = []) {
  let data = new FormData();

  let files = filesIgnore;

  Object.entries(formData).forEach(([key, value]) => {
    if (typeof value === 'object' && !files.includes(key)) {
      data.append(key, JSON.stringify(value) || null);
    } else if (files.includes(key)) {
      data.append(key, value[0] || null);
    } else {
      data.append(key, value || null);
    }
  })

  return data;
}

How does it work? It will convert and return all properties expect File objects that you've set in the ignore list (2nd argument. If anyone could tell me a better way to determine this that would help!) into a json string using JSON.stringify. Then on your server you'll just need to convert it back into a JSON object.

Example:

let form = {
  first_name: 'John',
  last_name: 'Doe',
  details: {
    phone_number: 1234 5678 910,
    address: '123 Some Street',
  },
  profile_picture: [object FileList] // set by your form file input. Currently only support 1 file per property.
}

function submit() {
  let data = formData(form, ['profile_picture']);

  axios.post('/url', data).then(res => {
    console.log('object uploaded');
  })
}

I am still kinda new to Http requests and JavaScript so any feedback would be highly appreciated!

I used this for Post my object data as Form Data.

const encodeData = require('querystring');

const object = {type: 'Authorization', username: 'test', password: '123456'};

console.log(object);
console.log(encodeData.stringify(object));

I had a scenario where nested JSON had to be serialised in a linear fashion while form data is constructed, since this is how server expects values. So, I wrote a small recursive function which translates the JSON which is like this:

{
   "orderPrice":"11",
   "cardNumber":"************1234",
   "id":"8796191359018",
   "accountHolderName":"Raj Pawan",
   "expiryMonth":"02",
   "expiryYear":"2019",
   "issueNumber":null,
   "billingAddress":{
      "city":"Wonderland",
      "code":"8796682911767",
      "firstname":"Raj Pawan",
      "lastname":"Gumdal",
      "line1":"Addr Line 1",
      "line2":null,
      "state":"US-AS",
      "region":{
         "isocode":"US-AS"
      },
      "zip":"76767-6776"
   }
}

Into something like this:

{
   "orderPrice":"11",
   "cardNumber":"************1234",
   "id":"8796191359018",
   "accountHolderName":"Raj Pawan",
   "expiryMonth":"02",
   "expiryYear":"2019",
   "issueNumber":null,
   "billingAddress.city":"Wonderland",
   "billingAddress.code":"8796682911767",
   "billingAddress.firstname":"Raj Pawan",
   "billingAddress.lastname":"Gumdal",
   "billingAddress.line1":"Addr Line 1",
   "billingAddress.line2":null,
   "billingAddress.state":"US-AS",
   "billingAddress.region.isocode":"US-AS",
   "billingAddress.zip":"76767-6776"
}

The server would accept form data which is in this converted format.

Here is the function:

function jsonToFormData (inJSON, inTestJSON, inFormData, parentKey) {
    // http://stackoverflow.com/a/22783314/260665
    // Raj: Converts any nested JSON to formData.
    var form_data = inFormData || new FormData();
    var testJSON = inTestJSON || {};
    for ( var key in inJSON ) {
        // 1. If it is a recursion, then key has to be constructed like "parent.child" where parent JSON contains a child JSON
        // 2. Perform append data only if the value for key is not a JSON, recurse otherwise!
        var constructedKey = key;
        if (parentKey) {
            constructedKey = parentKey + "." + key;
        }

        var value = inJSON[key];
        if (value && value.constructor === {}.constructor) {
            // This is a JSON, we now need to recurse!
            jsonToFormData (value, testJSON, form_data, constructedKey);
        } else {
            form_data.append(constructedKey, inJSON[key]);
            testJSON[constructedKey] = inJSON[key];
        }
    }
    return form_data;
}

Invocation:

        var testJSON = {};
        var form_data = jsonToFormData (jsonForPost, testJSON);

I am using testJSON just to see the converted results since I would not be able to extract the contents of form_data. AJAX post call:

        $.ajax({
            type: "POST",
            url: somePostURL,
            data: form_data,
            processData : false,
            contentType : false,
            success: function (data) {
            },
            error: function (e) {
            }
        });

Sorry for a late answer, but I was struggling with this as Angular 2 currently does not support file upload. So, the way to do it was sending a XMLHttpRequest with FormData. So, I created a function to do it. I'm using Typescript. To convert it to Javascript just remove data types declaration.

/**
     * Transforms the json data into form data.
     *
     * Example:
     *
     * Input:
     * 
     * fd = new FormData();
     * dob = {
     *  name: 'phone',
     *  photos: ['myphoto.jpg', 'myotherphoto.png'],
     *  price: '615.99',
     *  color: {
     *      front: 'red',
     *      back: 'blue'
     *  },
     *  buttons: ['power', 'volup', 'voldown'],
     *  cameras: [{
     *      name: 'front',
     *      res: '5Mpx'
     *  },{
     *      name: 'back',
     *      res: '10Mpx'
     *  }]
     * };
     * Say we want to replace 'myotherphoto.png'. We'll have this 'fob'.
     * fob = {
     *  photos: [null, <File object>]
     * };
     * Say we want to wrap the object (Rails way):
     * p = 'product';
     *
     * Output:
     *
     * 'fd' object updated. Now it will have these key-values "<key>, <value>":
     *
     * product[name], phone
     * product[photos][], myphoto.jpg
     * product[photos][], <File object>
     * product[color][front], red
     * product[color][back], blue
     * product[buttons][], power
     * product[buttons][], volup
     * product[buttons][], voldown
     * product[cameras][][name], front
     * product[cameras][][res], 5Mpx
     * product[cameras][][name], back
     * product[cameras][][res], 10Mpx
     * 
     * @param {FormData}  fd  FormData object where items will be appended to.
     * @param {Object}    dob Data object where items will be read from.
     * @param {Object =   null} fob File object where items will override dob's.
     * @param {string =   ''} p Prefix. Useful for wrapping objects and necessary for internal use (as this is a recursive method).
     */
    append(fd: FormData, dob: Object, fob: Object = null, p: string = ''){
        let apnd = this.append;

        function isObj(dob, fob, p){
            if(typeof dob == "object"){
                if(!!dob && dob.constructor === Array){
                    p += '[]';
                    for(let i = 0; i < dob.length; i++){
                        let aux_fob = !!fob ? fob[i] : fob;
                        isObj(dob[i], aux_fob, p);
                    }
                } else {
                    apnd(fd, dob, fob, p);
                }
            } else {
                let value = !!fob ? fob : dob;
                fd.append(p, value);
            }
        }

        for(let prop in dob){
            let aux_p = p == '' ? prop : `${p}[${prop}]`;
            let aux_fob = !!fob ? fob[prop] : fob;
            isObj(dob[prop], aux_fob, aux_p);
        }
    }

With ES6 and a more functional programming approach @adeneo's answer could looks like this:

function getFormData(object) {
    const formData = new FormData();
    Object.keys(object).forEach(key => formData.append(key, object[key]));
    return formData;
}

And alternatively using .reduce() and arrow-functions:

const getFormData = object => Object.keys(object).reduce((formData, key) => {
    formData.append(key, object[key]);
    return formData;
}, new FormData());

You can simply use:

formData.append('item', JSON.stringify(item));

Try JSON.stringify function as below

var postData = JSON.stringify(item);
var formData = new FormData();
formData.append("postData",postData );

The other answers were incomplete for me. I started from @Vladimir Novopashin answer and modified it. Here are the things, that I needed and bug I found:

• Support for file
• Support for array
• Bug: File inside complex object needs to be added with .prop instead of [prop]. For example, formData.append('photos[0][file]', file) didn't work on google chrome, while formData.append('photos[0].file', file) worked
• Ignore some properties in my object

The following code should work on IE11 and evergreen browsers.

function objectToFormData(obj, rootName, ignoreList) {
    var formData = new FormData();

    function appendFormData(data, root) {
        if (!ignore(root)) {
            root = root || '';
            if (data instanceof File) {
                formData.append(root, data);
            } else if (Array.isArray(data)) {
                for (var i = 0; i < data.length; i++) {
                    appendFormData(data[i], root + '[' + i + ']');
                }
            } else if (typeof data === 'object' && data) {
                for (var key in data) {
                    if (data.hasOwnProperty(key)) {
                        if (root === '') {
                            appendFormData(data[key], key);
                        } else {
                            appendFormData(data[key], root + '.' + key);
                        }
                    }
                }
            } else {
                if (data !== null && typeof data !== 'undefined') {
                    formData.append(root, data);
                }
            }
        }
    }

    function ignore(root){
        return Array.isArray(ignoreList)
            && ignoreList.some(function(x) { return x === root; });
    }

    appendFormData(obj, rootName);

    return formData;
}

Try obj2fd => https://www.npmjs.com/package/obj2fd

import obj2fd from 'obj2fd'

let data = {a:1, b:2, c:{ca:1}};
let dataWithFormData = obj2fd(data);
//result => [a=>1, b=>2, c=>[ca=>1]]

Maybe you're looking for this, a code that receive your javascript object, create a FormData object from it and then POST it to your server using new Fetch API:

    let myJsObj = {'someIndex': 'a value'};

    let datos = new FormData();
    for (let i in myJsObj){
        datos.append( i, myJsObj[i] );
    }

    fetch('your.php', {
        method: 'POST',
        body: datos
    }).then(response => response.json())
        .then(objson => {
            console.log('Success:', objson);
        })
        .catch((error) => {
            console.error('Error:', error);
        });