Convert JS Object to form data

Question

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 valu

Answer 1

This method convert a JS object to a FormData :

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

            return acc;
        }, new FormData());
}

Answer 2

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); 

Answer 3

If you have an object, you can easily create a FormData object and append the names and values from that object to formData.

You haven't posted any code, so it's a general example;

var form_data = new FormData();

for ( var key in item ) {
    form_data.append(key, item[key]);
}

$.ajax({
    url         : 'http://example.com/upload.php',
    data        : form_data,
    processData : false,
    contentType : false,
    type: 'POST'
}).done(function(data){
    // do stuff
});

There are more examples in the documentation on MDN

Answer 4

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());

Answer 5

• 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)
})

Answer 6

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));