React.js Image Upload
Uploading images basically is a two-step process:
Select a File
Before we can upload it, we have to select a file.
To allow the user to pick a file, we have to add <input type="file"> to our component JSX code. We also have to listen to any changes to that file. Such a change handler will trigger whenever the user picks a new file.
Like this:
<input type="file"
<button
We now need the two handler methods in our React component:
fileChangedHandler = (event) => {
const file = event.target.files[0]
}
uploadHandler = () => { ... }
To upload the file, we should store it in our state:
state = { selectedFile: null }
fileChangedHandler = event => {
this.setState({ selectedFile: event.target.files[0] })
}
uploadHandler = () => {
console.log(this.state.selectedFile)
}
Send the File to a Server
With the file stored in state, we can send it to a server.
For this, you can use axios. You can either send the file as binary data or wrapped in a FormData object - depending on what your REST API expects.
Send as binary data
uploadHandler = () => {
axios.post('my-domain.com/file-upload', this.state.selectedFile)
}
Send as FormData
uploadHandler = () => {
const formData = new FormData()
formData.append(
'myFile',
this.state.selectedFile,
this.state.selectedFile.name
)
axios.post('my-domain.com/file-upload', formData)
}
Show upload progress
In both cases, you can also output the upload progress if you want to.
uploadHandler = () => {
...
axios.post('my-domain.com/file-upload', formData, {
onUploadProgress: progressEvent => {
console.log(progressEvent.loaded / progressEvent.total)
}
})
}