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I am building an image upload form using Next.js/React.js, and I want the user to be able to assign a tag to each upload. I also want to show the image preview using 'URL.createObjectURL'. The uploading works fine, but on the upload page where I try to iterate through the list of images to show the preview and show an input box to assign the tag, none of this is showing. I cannot work out why.
The code:
import { useState } from "react";
import Head from 'next/head'
import Layout, { siteTitle } from '../../ponents/layout'
import Image from 'next/image'
export default function PrivatePage(props) {
const [images, setImages] = useState([])
const [imageURLS, setImageURLS] = useState([])
const [tag, setTag] = useState(null)
const uploadImageToClient = (event) => {
var imageList = images
var urlList = imageURLS
if (event.target.files && event.target.files[0]) {
imageList.push(event.target.files[0]);
urlList.push(URL.createObjectURL(event.target.files[0]))
setImages(imageList);
setImageURLS(urlList);
}
};
const uploadTagToClient = (event) => {
if (event.target.value) {
const i = event.target.value;
setTag(i);
}
};
const uploadToServer = async (event) => {
const body = new FormData()
images.map((file, index) => {
body.append(`file${index}`, file);
});
body.append("tag", tag)
const response = await fetch("/api/file", {
method: "POST",
body
});
};
return (
<Layout home>
<Head>
<title>{siteTitle}</title>
</Head>
<div className="container">
<div className="row">
<h4>Select Images</h4>
<div className="col">
<input type="file" className="btn btn-outline-success-inverse" onChange={uploadImageToClient} />
<input type="file" className="btn btn-outline-success-inverse" onChange={uploadImageToClient} />
</div>
<div className="col">
</div>
<button
className="btn btn-outline-success-inverse"
type="submit"
onClick={uploadToServer}
>
Send to server
</button>
{images.map((file, index) => {
return (
<div class="row ">
<lead>{file.name}</lead>
<input type="text" onChange={uploadTagToClient} />
<image src={imageURLS[index]}/>
</div>)
})}
</div>
</div>
</Layout>
);
}
To clarify, nothing inside images.map is showing when I select images.
I am building an image upload form using Next.js/React.js, and I want the user to be able to assign a tag to each upload. I also want to show the image preview using 'URL.createObjectURL'. The uploading works fine, but on the upload page where I try to iterate through the list of images to show the preview and show an input box to assign the tag, none of this is showing. I cannot work out why.
The code:
import { useState } from "react";
import Head from 'next/head'
import Layout, { siteTitle } from '../../ponents/layout'
import Image from 'next/image'
export default function PrivatePage(props) {
const [images, setImages] = useState([])
const [imageURLS, setImageURLS] = useState([])
const [tag, setTag] = useState(null)
const uploadImageToClient = (event) => {
var imageList = images
var urlList = imageURLS
if (event.target.files && event.target.files[0]) {
imageList.push(event.target.files[0]);
urlList.push(URL.createObjectURL(event.target.files[0]))
setImages(imageList);
setImageURLS(urlList);
}
};
const uploadTagToClient = (event) => {
if (event.target.value) {
const i = event.target.value;
setTag(i);
}
};
const uploadToServer = async (event) => {
const body = new FormData()
images.map((file, index) => {
body.append(`file${index}`, file);
});
body.append("tag", tag)
const response = await fetch("/api/file", {
method: "POST",
body
});
};
return (
<Layout home>
<Head>
<title>{siteTitle}</title>
</Head>
<div className="container">
<div className="row">
<h4>Select Images</h4>
<div className="col">
<input type="file" className="btn btn-outline-success-inverse" onChange={uploadImageToClient} />
<input type="file" className="btn btn-outline-success-inverse" onChange={uploadImageToClient} />
</div>
<div className="col">
</div>
<button
className="btn btn-outline-success-inverse"
type="submit"
onClick={uploadToServer}
>
Send to server
</button>
{images.map((file, index) => {
return (
<div class="row ">
<lead>{file.name}</lead>
<input type="text" onChange={uploadTagToClient} />
<image src={imageURLS[index]}/>
</div>)
})}
</div>
</div>
</Layout>
);
}
To clarify, nothing inside images.map is showing when I select images.
- What should be the type of event in TypeScript? – Ala Eddine Menai Commented Mar 5, 2024 at 9:56
2 Answers
Reset to default 3The issue happens because you're mutating the arrays you have in state with imageList.push and urlList.push which React doesn't pick up. This means state doesn't actually get updated and a re-render doesn't occur.
To fix it, rather than mutating those state arrays you need to create new ones when updating them.
const uploadImageToClient = (event) => {
if (event.target.files && event.target.files[0]) {
setImages((imageList) => [...imageList, event.target.files[0]]);
setImageURLS((urlList) => [
...urlList,
URL.createObjectURL(event.target.files[0])
]);
}
};
Unrelated to the main issue, you have several minor issues inside the render part of your ponent, specifically inside images.map.
- You need to set a
keyprop on the outer<div>element; - The
<lead>element doesn't exist, and needs to be replaced with a valid element; - The
<image>element also doesn't exist, you probably meant<img>or<Image>(fromnext/image).
You can handle image upload with multiple image preview with following code.
const handleFile = (e) => {
setMessage("");
let file = e.target.files;
for (let i = 0; i < file.length; i++) {
const fileType = file[i]['type'];
const validImageTypes = ['image/gif', 'image/jpeg', 'image/png'];
if (validImageTypes.includes(fileType)) {
setFile([...files,file[i]]);
} else {
setMessage("only images accepted");
}
}
};
Follow this snippet https://bbbootstrap./snippets/multiple-image-upload-preview-and-remove-92816546
本文标签： javascriptHow to show image upload previews with ReactStack Overflow
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