What File Am I to Upload Uber Documents in
In this mail service, we'll learn nigh the FormData interface available in mod spider web browsers equally a part of the HTML5 spec.
Nosotros'll see examples of using FormData with Ajax, Angular 7, Ionic and React.
What'south FormData
FormData is merely a data construction that tin be used to store key-value pairs. Just like its proper noun suggests information technology'due south designed for holding forms data i.e you lot can use it with JavaScript to build an object that corresponds to an HTML grade. It's mostly useful when yous need to transport form data to RESTful API endpoints, for instance to upload unmarried or multiple files using the XMLHttpRequest interface, the fetch() API or Axios.
You tin create a FormData object by instantiating the FormData interface using the new operator as follows:
const formData = new FormData() The formData reference refers to an instance of FormData. You tin can call many methods on the object to add together and work with pairs of data. Each pair has a primal and value.
These are the available methods on FormData objects:
-
suspend(): used to suspend a key-value pair to the object. If the key already exists, the value is appended to the original value for that key, -
delete(): used to deletes a key-value pair, -
entries(): returns an Iterator object that you can use to loop through the list the cardinal value pairs in the object, -
get(): used to return the value for a primal. If multiple values are appended, information technology returns the first value, -
getAll(): used to render all the values for a specified key, -
has(): used to check if there's a key, -
keys(): returns an Iterator object which you can use to listing the bachelor keys in the object, -
set(): used to add a value to the object, with the specified key. This is going to relace the value if a key already exists, -
values(): returns an Iterator object for the values of the FormData object.
File Upload Example with Vanilla JavaScript
Permit's now come across a uncomplicated example of file upload using vanilla JavaScript, XMLHttpRequest and FormData.
Navigate to your working binder and create and index.html file with the post-obit content:
<!DOCTYPE html> <html> <head> <title>Parcel Sandbox</title> <meta charset="UTF-viii" /> </head> <body> <div id="app"></div> <script src="index.js"> </script> </body> </html> We simply create an HTML document with a <div> identified past the app ID. Side by side, nosotros include the index.js file using a <script> tag.
Side by side, create the alphabetize.js file and add following code:
document.getElementById("app").innerHTML = ` <h1>File Upload & FormData Example</h1> <div> <input type="file" id="fileInput" /> </div> `; const fileInput = document.querySelector("#fileInput"); const uploadFile = file => { console.log("Uploading file..."); const API_ENDPOINT = "https://file.io"; const asking = new XMLHttpRequest(); const formData = new FormData(); request.open up("POST", API_ENDPOINT, true); request.onreadystatechange = () => { if (request.readyState === 4 && asking.status === 200) { console.log(request.responseText); } }; formData.suspend("file", file); request.ship(formData); }; fileInput.addEventListener("change", effect => { const files = event.target.files; uploadFile(files[0]); }); Nosotros kickoff insert an <input type="file" id="fileInput" /> element in our HTML folio. This will be used to select the file that we'll be uploading.
Next, nosotros query for the file input chemical element using the querySelector() method.
Next, we define the uploadFile() method in which nosotros kickoff declare anAPI_ENDPOINT variable that holds the accost of our file uploading endpoint. Next, we create an XMLHttpRequest request and an empty FormData object.
We employ the append method of FormData to append the file, passed as a parameter to the uploadFile() method, to the file key. This will create a key-value pair with file as a key and the content of the passed file every bit a value.
Next, we ship the request using the transport() method of XMLHttpRequest and nosotros pass in the FormData object every bit an argument.
Subsequently defining the uploadFile() method, nosotros listen for the change event on the <input> chemical element and we call theuploadFile() method with the selected file equally an argument. The file is accessed from event.target.files array.
You tin experiment with this instance from this code sandbox:
Uploading Multiple Files
Y'all can easily modify the code above to support multiple file uploading.
First, you lot need to add together the multiple property to the <input> element:
<input blazon="file" id="fileInput" multiple /> Now, you'll exist able to select multiple files from your bulldoze.
Side by side, change the uploadFile() method to accept an array of files as an argument and simply loop through the array and suspend the files to the FormData object:
const uploadFile = (files) => { console.log("Uploading file..."); const API_ENDPOINT = "https://file.io"; const asking = new XMLHttpRequest(); const formData = new FormData(); request.open("Mail", API_ENDPOINT, true); request.onreadystatechange = () => { if (request.readyState === 4 && request.status === 200) { console.log(request.responseText); } }; for (let i = 0; i < files.length; i++) { formData.suspend(files[i].proper noun, files[i]) } asking.ship(formData); }; Finally, phone call the method with an assortment of files as statement:
fileInput.addEventListener("change", upshot => { const files = result.target.files; uploadFile(files); }); Next, you tin check out these advanced tutorials for how to use FormData with Angular, Ionic and React:
- How to Post FormData with Angular seven
- React & Axios FormData
- Multiple File Upload with Ionic 4 & FormData
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Source: https://www.freecodecamp.org/news/formdata-explained/
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