效果图
老规矩先上效果图
先介绍一下H5中FileReader的一些方法以及事件
FileReader方法
| 名称 |
作用 |
| about() |
终止读取 |
| readAsBinaryString(file) |
将文件读取为二进制编码 |
| readAsDataURL(file) |
将文件读取为DataURL编码 |
| readAsText(file, [encoding]) |
将文件读取为文本 |
| readAsArrayBuffer(file) |
将文件读取为arraybuffer |
FileReader事件
| 名称 |
作用 |
| onloadstart |
读取开始时触发 |
| onprogress |
读取中 |
| onloadend |
读取完成触发，无论成功或失败 |
| onload |
文件读取成功完成时触发 |
| onabort |
中断时触发 |
| onerror |
出错时触发 |
代码
分布读取文件核心思想, 将文件分块以每M进行读取.
HTML部分
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<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<form>
<fieldset>
<legend>分步读取文件：</legend>
<input type="file" id="File">
<input type="button" value="中断" id="Abort">
<p>
<lable>读取进度：</lable>
<progress id="Progress" value="0" max="100"></progress>
</p>
</fieldset>
</form>
<script src="./loadFile.js"></script>
<script>
var progress = document.getElementById('Progress');
var events = {
load: function () {
console.log('loaded');
},
progress: function (percent) {
console.log(percent);
progress.value = percent;
},
success: function () {
console.log('success');
}
};
var loader;
document.getElementById('File').onchange = function (e) {
var file = this.files[0];
console.log(file)
loader = new FileLoader(file, events);
};
大专栏 HTML5 FileReader分布读取文件以及其方法简介r/> document.getElementById('Abort').onclick = function () {
loader.abort();
}
</script>
</body>
</html>
|
loadFile.js部分
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var FileLoader = function (file, events) {
this.reader = new FileReader();
this.file = file;
this.loaded = 0;
this.total = file.size;
this.step = 1024 * 1024;
this.events = events || {};
this.readBlob(0);
this.bindEvent();
}
FileLoader.prototype = {
bindEvent: function (events) {
var _this = this,
reader = this.reader;
reader.onload = function (e) {
_this.onLoad();
};
reader.onprogress = function (e) {
_this.onProgress(e.loaded);
};
},
onProgress: function (loaded) {
var percent,
handler = this.events.progress;
this.loaded += loaded;
percent = (this.loaded / this.total) * 100;
handler && handler(percent);
},
onLoad: function () {
var handler = this.events.load;
handler && handler(this.reader.result);
if (this.loaded < this.total) {
this.readBlob(this.loaded);
} else {
this.loaded = this.total;
this.events.success && this.events.success();
}
},
readBlob: function (start) {
var blob,
file = this.file;
if (file.slice) {
blob = file.slice(start, start + this.step);
} else {
blob = file;
}
this.reader.readAsText(blob);
},
abort: function () {
var reader = this.reader;
if(reader) {
reader.abort();
}
}
}
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