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但它似乎没有工作。有人可以帮忙吗？
function analyze(){
var f = new FileReader();
f.onloadend = function(){
console.log("success");
}
f.readAsText("cities.txt");
}
是的，有可能使用FileReader，我已经做了一个这样的例子，这里是代码：
<!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IE的一些旧版本（我认为6-8），我有一些旧的代码也可以这样做但是 它已经有一段时间了，所以我不得不把它挖出来 我找到了一个类似于我用Jacky Cui's blog礼貌的解决方案并编辑了这个答案（也清理了一些代码）。希望能帮助到你。
最后，我刚刚阅读了其他一些让我参与抽奖的答案，但正如他们所建议的那样，您可能正在寻找允许您从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>
使用javascript XMLHttpRequest（）类（AJAX）可以非常轻松地完成此操作：
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" );
出于安全原因，Javascript无权访问用户的文件系统。 FileReader仅适用于用户手动选择的文件。
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>
（小提琴：https://jsfiddle.net/ya3ya6/7hfkdnrg/2/）
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;
});
}
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;
}