问题
How to convert HTML5 FormData object to JSON? Without Jquery and handling nested properties in FormData like a object.
回答1:
You could also use forEach on the FormData object directly:
var object = {};
formData.forEach(function(value, key){
object[key] = value;
});
var json = JSON.stringify(object);
UPDATE:
And for those who prefer the same solution with ES6 arrow functions:
var object = {};
formData.forEach((value, key) => {object[key] = value});
var json = JSON.stringify(object);
UPDATE 2:
And for those who want support for multi select lists or other form elements with multiple values (since there are so many comments below the answer regarding this issue I will add a possible solution):
var object = {};
formData.forEach((value, key) => {
if(!object.hasOwnProperty(key)){
object[key] = value;
return;
}
if(!Array.isArray(object[key])){
object[key] = [object[key]];
}
object[key].push(value);
});
var json = JSON.stringify(object);
Here a Fiddle demonstrating the use of this method with a simple multi select list.
UPDATE 3:
As a side note for those ending up here, in case the purpose of converting the form data to json is to send it through a XML HTTP request to a server you can send the FormData object directly without converting it. As simple as this:
var request = new XMLHttpRequest();
request.open("POST", "http://example.com/submitform.php");
request.send(formData);
See also Using FormData Objects on MDN for reference:
UPDATE 4:
As mentioned in one of the comments below my answer the JSON stringify method won't work out of the box for all types of objects. For more information on what types are supported I would like to refer to the Description section in the MDN documentation of JSON.stringify.
In the description is also mentioned that:
If the value has a toJSON() method, it's responsible to define what data will be serialized.
This means that you can supply your own toJSON serialization method with logic for serializing your custom objects. Like that you can quickly and easily build serialization support for more complex object trees.
回答2:
In 2019, this kind of task became super-easy.
JSON.stringify(Object.fromEntries(formData));
Object.fromEntries: Supported in Chrome 73+, Firefox 63+, Safari 12.1
回答3:
Here's a way to do it in a more functional style, without the use of a library.
Array.from(formData.entries()).reduce((memo, pair) => ({
...memo,
[pair[0]]: pair[1],
}), {});
Example:
document.getElementById('foobar').addEventListener('submit', (e) => {
e.preventDefault();
const formData = new FormData(e.target);
const data = Array.from(formData.entries()).reduce((memo, pair) => ({
...memo,
[pair[0]]: pair[1],
}), {});
document.getElementById('output').innerHTML = JSON.stringify(data);
});<form id='foobar'>
<input name='baz' />
<input type='submit' />
</form>
<pre id='output'>Input some value and submit</pre>回答4:
If you have multiple entries with the same name, for example if you use <SELECT multiple> or have multiple <INPUT type="checkbox"> with the same name, you need to take care of that and make an array of the value. Otherwise you only get the last selected value.
Here is the modern ES6-variant:
function formToJSON( elem ) {
let output = {};
new FormData( elem ).forEach(
( value, key ) => {
// Check if property already exist
if ( Object.prototype.hasOwnProperty.call( output, key ) ) {
let current = output[ key ];
if ( !Array.isArray( current ) ) {
// If it's not an array, convert it to an array.
current = output[ key ] = [ current ];
}
current.push( value ); // Add the new value to the array.
} else {
output[ key ] = value;
}
}
);
return JSON.stringify( output );
}
Slightly older code (but still not supported by IE11, since it doesn't support ForEach or entries on FormData)
function formToJSON( elem ) {
var current, entries, item, key, output, value;
output = {};
entries = new FormData( elem ).entries();
// Iterate over values, and assign to item.
while ( item = entries.next().value )
{
// assign to variables to make the code more readable.
key = item[0];
value = item[1];
// Check if key already exist
if (Object.prototype.hasOwnProperty.call( output, key)) {
current = output[ key ];
if ( !Array.isArray( current ) ) {
// If it's not an array, convert it to an array.
current = output[ key ] = [ current ];
}
current.push( value ); // Add the new value to the array.
} else {
output[ key ] = value;
}
}
return JSON.stringify( output );
}
回答5:
You can achieve this by using the FormData() object. This FormData object will be populated with the form's current keys/values using the name property of each element for the keys and their submitted value for the values. It will also encode file input content.
Example:
var myForm = document.getElementById('myForm');
myForm.addEventListener('submit', function(event)
{
event.preventDefault();
var formData = new FormData(myForm),
result = {};
for (var entry of formData.entries())
{
result[entry[0]] = entry[1];
}
result = JSON.stringify(result)
console.log(result);
});
回答6:
Easy To Use Function
I Have Created A Function For This
function FormDataToJSON(FormElement){
var formData = new FormData(FormElement);
var ConvertedJSON= {};
for (const [key, value] of formData.entries())
{
ConvertedJSON[key] = value;
}
return ConvertedJSON
}
Example Usage
var ReceivedJSON = FormDataToJSON(document.getElementById('FormId');)
In this code I have created empty JSON variable using for loop I have used keys from formData Object to JSON Keys in every Itration.
You Find This Code In My JS Library On GitHub Do Suggest Me If It Needs Improvement I Have Placed Code Here https://github.com/alijamal14/Utilities/blob/master/Utilities.js
回答7:
FormData method .entries and the for of expression is not supported in IE11 and Safari.
Here is a simplier version to support Safari, Chrome, Firefox and Edge
function formDataToJSON(formElement) {
var formData = new FormData(formElement),
convertedJSON = {};
formData.forEach(function(value, key) {
convertedJSON[key] = value;
});
return convertedJSON;
}
Warning: this answer doesn't work in IE11.
FormData doesn't have a forEach method in IE11.
I'm still searching for a final solution to support all major browsers.
回答8:
This post is already a year old... but, I really, really like the ES6 @dzuc answer. However it is incomplete by not been able to handle multiple selects or checkboxes. This has already pointed and code solutions has been offered. I find them heavy and not optimized. So I wrote a 2 versions based on @dzuc to handle these cases:
- For ASP style forms where multiple items name could just simple repeated.
let r=Array.from(fd).reduce(
(o , [k,v]) => (
(!o[k])
? {...o , [k] : v}
: {...o , [k] : [...o[k] , v]}
)
,{}
);
let obj=JSON.stringify(r);
One line Hotshot version:
Array.from(fd).reduce((o,[k,v])=>((!o[k])?{...o,[k]:v}:{...o,[k]:[...o[k],v]}),{});
- For PHP style forms where the multiple item names must have a
[]suffix.
let r=Array.from(fd).reduce(
(o , [k,v]) => (
(k.split('[').length>1)
? (k=k.split('[')[0]
, (!o[k])
? {...o , [k] : [v]}
: {...o , [k] : [...o[k] , v ]}
)
: {...o , [k] : v}
)
,{}
);
let obj=JSON.stringify(r);
One line Hotshot version:
Array.from(fd).reduce((o,[k,v])=>((k.split('[').length>1)?(k=k.split('[')[0],(!o[k])?{...o,[k]:[v]}:{...o,[k]:[...o[k],v]}):{...o,[k]:v}),{});
- Extension of PHP form that support multi-level arrays.
Since last time I wrote the previous second case, at work it came a case that the PHP form has checkboxes on multi-levels. I wrote a new case to support previous case and this one. I created a snippet to better showcase this case, the result show on the console for this demo, modify this to your need. Tried to optimize it the best I could without compromising performance, however, it compromise some human readability. It takes advantage that arrays are objects and variables pointing to arrays are kept as reference. No hotshot for this one, be my guest.
let nosubmit = (e) => {
e.preventDefault();
const f = Array.from(new FormData(e.target));
const obj = f.reduce((o, [k, v]) => {
let a = v,
b, i,
m = k.split('['),
n = m[0],
l = m.length;
if (l > 1) {
a = b = o[n] || [];
for (i = 1; i < l; i++) {
m[i] = (m[i].split(']')[0] || b.length) * 1;
b = b[m[i]] = ((i + 1) == l) ? v : b[m[i]] || [];
}
}
return { ...o, [n]: a };
}, {});
console.log(obj);
}
document.querySelector('#theform').addEventListener('submit', nosubmit, {capture: true});<h1>Multilevel Form</h1>
<form action="#" method="POST" enctype="multipart/form-data" id="theform">
<input type="hidden" name="_id" value="93242" />
<input type="hidden" name="_fid" value="45c0ec96929bc0d39a904ab5c7af70ef" />
<label>Select:
<select name="uselect">
<option value="A">A</option>
<option value="B">B</option>
<option value="C">C</option>
</select>
</label>
<br /><br />
<label>Checkboxes one level:<br/>
<input name="c1[]" type="checkbox" checked value="1"/>v1
<input name="c1[]" type="checkbox" checked value="2"/>v2
<input name="c1[]" type="checkbox" checked value="3"/>v3
</label>
<br /><br />
<label>Checkboxes two levels:<br/>
<input name="c2[0][]" type="checkbox" checked value="4"/>0 v4
<input name="c2[0][]" type="checkbox" checked value="5"/>0 v5
<input name="c2[0][]" type="checkbox" checked value="6"/>0 v6
<br/>
<input name="c2[1][]" type="checkbox" checked value="7"/>1 v7
<input name="c2[1][]" type="checkbox" checked value="8"/>1 v8
<input name="c2[1][]" type="checkbox" checked value="9"/>1 v9
</label>
<br /><br />
<label>Radios:
<input type="radio" name="uradio" value="yes">YES
<input type="radio" name="uradio" checked value="no">NO
</label>
<br /><br />
<input type="submit" value="Submit" />
</form>回答9:
If you are using lodash it can be done concisely with fromPairs
import {fromPairs} from 'lodash';
const object = fromPairs(Array.from(formData.entries()));
回答10:
Even though the answer from @dzuc is already very good, you could use array destructuring (available in modern browsers or with Babel) to make it even a bit more elegant:
// original version from @dzuc
const data = Array.from(formData.entries())
.reduce((memo, pair) => ({
...memo,
[pair[0]: pair[1],
}), {})
// with array destructuring
const data = Array.from(formData.entries())
.reduce((memo,[key, value]) => ({
...memo,
[key]: value,
}), {})
回答11:
You can try this
formDataToJSON($('#form_example'));
# Create a function to convert the serialize and convert the form data
# to JSON
# @param : $('#form_example');
# @return a JSON Stringify
function formDataToJSON(form) {
let obj = {};
let formData = form.serialize();
let formArray = formData.split("&");
for (inputData of formArray){
let dataTmp = inputData.split('=');
obj[dataTmp[0]] = dataTmp[1];
}
return JSON.stringify(obj);
}
回答12:
If the following items meet your needs, you're in luck:
- You want to convert an array of arrays like
[['key','value1'], ['key2','value2'](like what FormData gives you) into a key->value object like{key1: 'value1', key2: 'value2'}and the convert it to a JSON string. - You are targeting browsers/devices with the latest ES6 interpreter or are compiling with something like babel.
- You want the tiniest way to accomplish this.
Here is the code you'll need:
const data = new FormData(document.querySelector('form'));
const json = JSON.stringify(Array.from(data).reduce((o,[k,v])=>(o[k]=v,o),{}));
Hope this helps someone.
回答13:
Abusive one-liner!
Array.from(fd).reduce((obj, [k, v]) => ({...obj, [k]: v}), {});
Today I learned firefox has object spread support and array destructuring!
回答14:
Worked for me
var myForm = document.getElementById("form");
var formData = new FormData(myForm),
obj = {};
for (var entry of formData.entries()){
obj[entry[0]] = entry[1];
}
console.log(obj);
回答15:
In my case form Data was data , fire base was expecting an object but data contains object as well as all other stuffs so i tried data.value it worked!!!
来源：https://stackoverflow.com/questions/41431322/how-to-convert-formdatahtml5-object-to-json