[React] Upload 上傳文字檔，與讀檔FileReader

react filereader

nlstudio 2023-05-03 12:43:46 ‧ 838 瀏覽

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在原生 JS我們可以這樣寫

</head>
 
 <body>
    <input type='file' onchange='onChooseFile(event)' />
 </body> 
 <script type="text/javascript">
    function onChooseFile(event) {
        if (typeof window.FileReader !== 'function')
            throw ("The file API isn't supported on this browser.");
        let input = event.target;
        if (!input)
            throw ("The browser does not properly implement the event object");
        if (!input.files)
            throw ("This browser does not support the `files` property of the file input.");
        if (!input.files[0])
            return undefined;
        let file = input.files[0];
        let fr = new FileReader();
        fr.onload = funResult;
        fr.readAsText(file);
    }
    function funResult(event){
        console.log( event.target.result)
    }
</script>
<html>

React

//選擇檔案部份
//使用.bind(this) 使用箭頭函數( () => {}) 使最後一個作用域 ( this) 保持原樣 
<input type="file" name="myFile" onChange={this.FileUploadHandler.bind(this)} />

//讀取文檔後文字存放的input 
<input type="text" id="" name="" value={this.state.fileText} onChange={(event)=>this.setState({fileText:event.target.value})}/>

    FileUploadHandler(event) {
        if (typeof window.FileReader !== 'function')
            throw ("The file API isn't supported on this browser.");
        let input = event.target;
        if (!input)
            throw ("The browser does not properly implement the event object");
        if (!input.files)
            throw ("This browser does not support the `files` property of the file input.");
        if (!input.files[0])
            return undefined;
        let file = input.files[0]
        let fr = new FileReader()
        fr.onload = (e)=> {
            //this.setState({ fileText : e.target.result });
            console.log(e.target.result)
            this.setState({fileText:e.target.result})
        }
        fr.readAsText(file)
    }