59

我正在尝试将文本文件加载到我的 JavaScript 文件中,然后从该文件中读取行以获取信息,我尝试了 FileReader,但它似乎不起作用。任何人都可以帮忙吗?

function analyze(){
   var f = new FileReader();

   f.onloadend = function(){
       console.log("success");
   }
   f.readAsText("cities.txt");
}
4

5 回答 5

60

是的,使用 FileReader 是可能的,我已经做了一个例子,下面是代码:

<!DOCTYPE html>
<html>
  <head>
    <title>Read File (via User Input selection)</title>
    <script type="text/javascript">
    var reader; //GLOBAL File Reader object for demo purpose only

    /**
     * Check for the various File API support.
     */
    function checkFileAPI() {
        if (window.File && window.FileReader && window.FileList && window.Blob) {
            reader = new FileReader();
            return true; 
        } else {
            alert('The File APIs are not fully supported by your browser. Fallback required.');
            return false;
        }
    }

    /**
     * read text input
     */
    function readText(filePath) {
        var output = ""; //placeholder for text output
        if(filePath.files && filePath.files[0]) {           
            reader.onload = function (e) {
                output = e.target.result;
                displayContents(output);
            };//end onload()
            reader.readAsText(filePath.files[0]);
        }//end if html5 filelist support
        else if(ActiveXObject && filePath) { //fallback to IE 6-8 support via ActiveX
            try {
                reader = new ActiveXObject("Scripting.FileSystemObject");
                var file = reader.OpenTextFile(filePath, 1); //ActiveX File Object
                output = file.ReadAll(); //text contents of file
                file.Close(); //close file "input stream"
                displayContents(output);
            } catch (e) {
                if (e.number == -2146827859) {
                    alert('Unable to access local files due to browser security settings. ' + 
                     'To overcome this, go to Tools->Internet Options->Security->Custom Level. ' + 
                     'Find the setting for "Initialize and script ActiveX controls not marked as safe" and change it to "Enable" or "Prompt"'); 
                }
            }       
        }
        else { //this is where you could fallback to Java Applet, Flash or similar
            return false;
        }       
        return true;
    }   

    /**
     * display content using a basic HTML replacement
     */
    function displayContents(txt) {
        var el = document.getElementById('main'); 
        el.innerHTML = txt; //display output in DOM
    }   
</script>
</head>
<body onload="checkFileAPI();">
    <div id="container">    
        <input type="file" onchange='readText(this)' />
        <br/>
        <hr/>   
        <h3>Contents of the Text file:</h3>
        <div id="main">
            ...
        </div>
    </div>
</body>
</html>

也可以使用 ActiveX 对象做同样的事情来支持一些旧版本的 IE(我认为是 6-8),我有一些旧代码也可以做到这一点,但已经有一段时间了,所以我必须挖掘它我找到了一个类似于我在Jacky Cui 的博客中使用的解决方案并编辑了这个答案(也稍微清理了代码)。希望能帮助到你。

最后,我刚刚阅读了一些其他让我脱颖而出的答案,但正如他们所建议的那样,您可能正在寻找可让您从 JavaScript 文件所在的服务器(或设备)加载文本文件的代码。如果是这种情况,那么您希望 AJAX 代码动态加载文档,如下所示:

<!DOCTYPE html>
<html>
<head><meta charset="utf-8" />
<title>Read File (via AJAX)</title>
<script type="text/javascript">
var reader = new XMLHttpRequest() || new ActiveXObject('MSXML2.XMLHTTP');

function loadFile() {
    reader.open('get', 'test.txt', true); 
    reader.onreadystatechange = displayContents;
    reader.send(null);
}

function displayContents() {
    if(reader.readyState==4) {
        var el = document.getElementById('main');
        el.innerHTML = reader.responseText;
    }
}

</script>
</head>
<body>
<div id="container">
    <input type="button" value="test.txt"  onclick="loadFile()" />
    <div id="main">
    </div>
</div>
</body>
</html>
于 2012-12-04T18:38:05.600 回答
13

这可以使用 javascript XMLHttpRequest() 类 (AJAX) 轻松完成:

function FileHelper()

{
    FileHelper.readStringFromFileAtPath = function(pathOfFileToReadFrom)
    {
        var request = new XMLHttpRequest();
        request.open("GET", pathOfFileToReadFrom, false);
        request.send(null);
        var returnValue = request.responseText;

        return returnValue;
    }
}

...

var text = FileHelper.readStringFromFileAtPath ( "mytext.txt" );
于 2014-03-03T16:05:19.747 回答
11

出于安全原因,Javascript 无法访问用户的文件系统。FileReader仅适用于用户手动选择的文件。

于 2012-12-04T18:31:47.293 回答
3

我的例子

<html>

<head>
  <link rel="stylesheet" href="http://code.jquery.com/ui/1.11.3/themes/smoothness/jquery-ui.css">
  <script src="http://code.jquery.com/jquery-1.10.2.js"></script>
  <script src="http://code.jquery.com/ui/1.11.3/jquery-ui.js"></script>
</head>

<body>
  <script>
    function PreviewText() {
      var oFReader = new FileReader();
      oFReader.readAsDataURL(document.getElementById("uploadText").files[0]);
      oFReader.onload = function(oFREvent) {
        document.getElementById("uploadTextValue").value = oFREvent.target.result;
        document.getElementById("obj").data = oFREvent.target.result;
      };
    };
    jQuery(document).ready(function() {
      $('#viewSource').click(function() {
        var text = $('#uploadTextValue').val();
        alert(text);
        //here ajax
      });
    });
  </script>
  <object width="100%" height="400" data="" id="obj"></object>
  <div>
    <input type="hidden" id="uploadTextValue" name="uploadTextValue" value="" />
    <input id="uploadText" style="width:120px" type="file" size="10" onchange="PreviewText();" />
  </div>
  <a href="#" id="viewSource">Source file</a>
</body>

</html>
于 2015-02-19T11:15:20.753 回答
2

(小提琴: https ://jsfiddle.net/ya3ya6/7hfkdnrg/2/ )

  1. 用法

html:

<textarea id='tbMain' ></textarea>
<a id='btnOpen' href='#' >Open</a>

JS:

document.getElementById('btnOpen').onclick = function(){
    openFile(function(txt){
        document.getElementById('tbMain').value = txt; 
    });
}
  1. Js 助手函数
function openFile(callBack){
  var element = document.createElement('input');
  element.setAttribute('type', "file");
  element.setAttribute('id', "btnOpenFile");
  element.onchange = function(){
      readText(this,callBack);
      document.body.removeChild(this);
      }

  element.style.display = 'none';
  document.body.appendChild(element);

  element.click();
}

function readText(filePath,callBack) {
    var reader;
    if (window.File && window.FileReader && window.FileList && window.Blob) {
        reader = new FileReader();
    } else {
        alert('The File APIs are not fully supported by your browser. Fallback required.');
        return false;
    }
    var output = ""; //placeholder for text output
    if(filePath.files && filePath.files[0]) {           
        reader.onload = function (e) {
            output = e.target.result;
            callBack(output);
        };//end onload()
        reader.readAsText(filePath.files[0]);
    }//end if html5 filelist support
    else { //this is where you could fallback to Java Applet, Flash or similar
        return false;
    }       
    return true;
}
于 2019-03-10T15:07:52.830 回答