Jquery File Upload Form Date How to
In this post, we'll learn virtually the FormData interface bachelor in modern spider web browsers equally a part of the HTML5 spec.
We'll see examples of using FormData with Ajax, Angular vii, Ionic and React.
What's FormData
FormData is simply a information structure that can be used to shop key-value pairs. Just like its proper name suggests it'due south designed for holding forms data i.e you can employ it with JavaScript to build an object that corresponds to an HTML form. It's mostly useful when yous need to ship form information to RESTful API endpoints, for instance to upload single or multiple files using the XMLHttpRequest interface, the fetch() API or Axios.
Yous can create a FormData object past instantiating the FormData interface using the new operator as follows:
const formData = new FormData() The formData reference refers to an instance of FormData. You can phone call many methods on the object to add and work with pairs of data. Each pair has a key and value.
These are the available methods on FormData objects:
-
append(): used to suspend a fundamental-value pair to the object. If the cardinal already exists, the value is appended to the original value for that fundamental, -
delete(): used to deletes a key-value pair, -
entries(): returns an Iterator object that yous can use to loop through the listing the cardinal value pairs in the object, -
become(): used to render the value for a primal. If multiple values are appended, it returns the first value, -
getAll(): used to return all the values for a specified key, -
has(): used to bank check if in that location'south a key, -
keys(): returns an Iterator object which yous can employ to list the available keys in the object, -
ready(): used to add a value to the object, with the specified primal. 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 Case with Vanilla JavaScript
Let's now run across a simple example of file upload using vanilla JavaScript, XMLHttpRequest and FormData.
Navigate to your working binder and create and index.html file with the following content:
<!DOCTYPE html> <html> <head> <championship>Packet Sandbox</title> <meta charset="UTF-8" /> </head> <body> <div id="app"></div> <script src="index.js"> </script> </body> </html> Nosotros simply create an HTML document with a <div> identified by the app ID. Next, nosotros include the index.js file using a <script> tag.
Next, create the index.js file and add together following code:
document.getElementById("app").innerHTML = ` <h1>File Upload & FormData Example</h1> <div> <input type="file" id="fileInput" /> </div> `; const fileInput = certificate.querySelector("#fileInput"); const uploadFile = file => { console.log("Uploading file..."); const API_ENDPOINT = "https://file.io"; const request = new XMLHttpRequest(); const formData = new FormData(); request.open up("POST", API_ENDPOINT, true); asking.onreadystatechange = () => { if (request.readyState === 4 && asking.status === 200) { console.log(request.responseText); } }; formData.append("file", file); asking.transport(formData); }; fileInput.addEventListener("alter", outcome => { const files = event.target.files; uploadFile(files[0]); }); We first 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, we query for the file input element using the querySelector() method.
Side by side, we define the uploadFile() method in which we first declare anAPI_ENDPOINT variable that holds the address of our file uploading endpoint. Next, we create an XMLHttpRequest request and an empty FormData object.
Nosotros apply the append method of FormData to append the file, passed every bit a parameter to the uploadFile() method, to the file key. This will create a primal-value pair with file equally a key and the content of the passed file as a value.
Next, nosotros ship the request using the send() method of XMLHttpRequest and we laissez passer in the FormData object as an argument.
Later defining the uploadFile() method, nosotros listen for the change consequence on the <input> element and we phone call theuploadFile() method with the selected file as an argument. The file is accessed from event.target.files array.
You can experiment with this example from this code sandbox:
Uploading Multiple Files
You lot tin easily modify the code above to support multiple file uploading.
First, you need to add the multiple property to the <input> element:
<input type="file" id="fileInput" multiple /> Now, you lot'll exist able to select multiple files from your drive.
Next, change the uploadFile() method to take an array of files as an argument and simply loop through the assortment and append 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(); asking.open("POST", API_ENDPOINT, true); request.onreadystatechange = () => { if (asking.readyState === 4 && request.status === 200) { console.log(asking.responseText); } }; for (let i = 0; i < files.length; i++) { formData.append(files[i].name, files[i]) } asking.send(formData); }; Finally, call the method with an array of files equally statement:
fileInput.addEventListener("change", event => { const files = effect.target.files; uploadFile(files); }); Next, you can cheque out these avant-garde 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 four & FormData
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Source: https://www.freecodecamp.org/news/formdata-explained/
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