我是新来的反应js。我想用react js异步上传图像 假设我有这段代码
convert.to.date <- function(d) {
if(is.na(strptime(d, '%Y-%m-%d %H:%M:%S'))) stop("Format incorrect")
return(format(d, format='%Y-%m-%d %H:%M:%S', usetz = FALSE))
}
convert.to.date('2002-09-04 16:45:40')
#[1] "2002-09-04 16:45:40"
convert.to.date('09-04-2002 16:45:40')
#Error in convert.to.date("09-04-2002 16:45:40") : Format incorrect
任何答案都将不胜感激!
答案 0 :(得分:9)
您可以使用FileReader
var FormBox = React.createClass({
getInitialState: function () {
return {
file: '',
imagePreviewUrl: ''
}
},
pressButton: function () {
e.preventDefault();
// TODO: do something with -> this.state.file
console.log('handle uploading-', this.state.file);
},
getPhoto: function (e) {
e.preventDefault();
let reader = new FileReader();
let file = e.target.files[0];
reader.onloadend = () => {
this.setState({
file: file,
imagePreviewUrl: reader.result
});
}
reader.readAsDataURL(file);
},
render: function () {
let {imagePreviewUrl} = this.state;
let imagePreview = null;
if (imagePreviewUrl) {
imagePreview = (<img src={imagePreviewUrl} />);
} else {
imagePreview = (<div className="previewText">Please select an Image for Preview</div>);
}
return (
<div>
<form action='.' enctype="multipart/form-data">
<input type='file' onChange={this.getPhoto}/>
<button onClick={this.pressButton}> Get it </button>
</form>
<div className="imgPreview">
{imagePreview}
</div>
</div>
)
}
})
ReactDOM.render(<FormBox />, document.getElementById('root'))
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.14.8/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.14.8/react-dom.min.js"></script>
<div id="root"></div>
答案 1 :(得分:1)
使用以下模块选择图像。
https://www.npmjs.com/package/react-image-uploader
然后,您可以使用xhr请求将图像上传到服务器。以下是示例代码。
var xhr = new XMLHttpRequest();
xhr.onload = function (e) {
//your success code goes here
}
var formData = new FormData();
xhr.open("POST", url, true);
formData.append('file', fileData);
xhr.send(formData);
var xhr = new XMLHttpRequest();
xhr.onload = function (e) {
//your success code goes here
}
var formData = new FormData();
xhr.open("POST", url, true);
formData.append('file', fileData);
xhr.send(formData);
答案 2 :(得分:1)
import axios from 'axios';
var FormBox = React.createClass({
getInitialState: function () {
return {
photo: [],
name : '',
documents:[]
}
},
pressButton: function () {
var component = this
var data = new FormData();
data.append("photo", component.state.photo, component.state.name);
var request = axios.post('http://localhost:3000/document', data)
request.then(function(response){
// you need to send data from server in response
if(response.status == 200){
console.log('saved in db')
component.state.documents.push(response.data.documents)
// pushed document data in documents array
}
})
},
getPhoto: function () {
var uploadfile = document.getElementById(upload_doc).files[0]
this.setState({
photo: uploadfile, name : uploadfile.name
})
},
render: function () {
var documents = this.state.documents.map((doc)=>{
return <div>
<a href={doc.url}>{doc.name}</a>
<img src={doc.photo} />
</div>
})
// you can show your documents uploaded this way using map function
return (
<form action='.' enctype="multipart/form-data">
<input type='file' id='upload_doc' onChange={this.getPhoto}/>
<button onClick={this.pressButton}> Get it </button>
<span>{documents}</span>
// this way you can see uploaded documents
</form>
)
}
})
ReactDOM.render(<FormBox />, document.getElementById('root'))
答案 3 :(得分:0)
使用axios节点模块 axios-fileupload
,这是一种更简单的方法
npm install --save axios-fileupload
const axiosFileupload = require('axios-fileupload');
axiosFileupload(url,file);
答案 4 :(得分:0)
您可以使用whatwg-fetch发帖请求。在pressButton()
功能中进行以下更改 -
import 'whatwg-fetch';
//....
pressButton: function (url) {
var data = new FormData();
data.append("photo", this.state.photo);
var options = {
body: data,
timeout: 3000 * 60 * 60
};
let callOptions = {
method : 'POST',
headers : {
'Content-Type': 'application/json'
},
body : JSON.stringify(options.body)
}
return fetch(url, callOptions).then(response => response.json());
}
答案 5 :(得分:0)
如果计划使用node和express上传文件,则必须同时创建服务器和客户端。服务器具有api,客户端将使用api通过axios上传文件。
首先,我们要放入四个包,分别是express,explicit-fileupload,cors和nodemon。运行以下命令以安装应用程序。
npm i express express-fileupload cors nodemon
现在,在您喜欢的代码编辑器中打开fileupload文件夹,并创建一个称为server.js的全新文档。
// server.js
const express = require('express');
const fileUpload = require('express-fileupload');
const cors = require('cors')
const app = express();
// middle ware
app.use(express.static('public')); //to access the files in public folder
app.use(cors()); // it enables all cors requests
app.use(fileUpload());
// file upload api
app.post('/upload', (req, res) => {
if (!req.files) {
return res.status(500).send({ msg: "file is not found" })
}
// accessing the file
const myFile = req.files.file;
// mv() method places the file inside public directory
myFile.mv(`${__dirname}/public/${myFile.name}`, function (err) {
if (err) {
console.log(err)
return res.status(500).send({ msg: "Error occured" });
}
// returing the response with file path and name
return res.send({name: myFile.name, path: `/${myFile.name}`});
});
})
app.listen(4500, () => {
console.log('server is running at port 4500');
})
使用node server.js
启动服务器运行。
在您喜欢的代码编辑器上打开react app文件夹,并在src文件夹中创建一个名为fileupload.js的全新报告。现在上传以下代码。
// fileupload.js
import React, { useRef, useState } from 'react';
import axios from 'axios';
function FileUpload() {
const [file, setFile] = useState(''); // storing the uploaded file
// storing the recived file from backend
const [data, getFile] = useState({ name: "", path: "" });
const [progress, setProgess] = useState(0); // progess bar
const el = useRef(); // accesing input element
const handleChange = (e) => {
setProgess(0)
const file = e.target.files[0]; // accesing file
console.log(file);
setFile(file); // storing file
}
const uploadFile = () => {
const formData = new FormData();
formData.append('file', file); // appending file
axios.post('http://localhost:4500/upload', formData, {
onUploadProgress: (ProgressEvent) => {
let progress = Math.round(
ProgressEvent.loaded / ProgressEvent.total * 100) + '%';
setProgess(progress);
}
}).then(res => {
console.log(res);
getFile({ name: res.data.name,
path: 'http://localhost:4500' + res.data.path
})
}).catch(err => console.log(err))}
return (
<div>
<div className="file-upload">
<input type="file" ref={el} onChange={handleChange} />
<div className="progessBar" style={{ width: progress }}>
{progress}
</div>
<button onClick={uploadFile} className="upbutton">
Upload
</button>
<hr />
{/* displaying received video*/}
{data.path && <video src={data.path} autoPlay controls />}
</div>
</div>
);
}
export default FileUpload;
现在将AppUp.js文件中的FileUpload组件导入。
// App.js
import React from 'react';
import FileUpload from './fileupload';
import './App.css';
function App() {
return (
<div className="App">
<FileUpload />
</div >
);
}
export default App;
通过运行npm start
启动react应用。