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Created May 29, 2014 06:23
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FileReader.prototype.readAsArrayBuffer vs FileReader.prototype.readAsDataUrl
Raw
index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>FileReader test</title>
</head>
<body>
<form action="">
<input type=file multiple accept="image/*"><br/>
<input type=submit value="Run test">
</form>
<div id="data-url-result"></div>
<div id="blob-result"></div>
<script src=test.js></script>
</body>
</html>
Raw
test.js
(function () {
if (!window.Promise || !window.URL || !window.FileReader || !window.Blob) {
return alert("There is not enought javascript support for run the tests");
}
document.addEventListener('DOMContentLoaded', function () {
var fileControl = document.querySelector('input[type=file]'),
testFormNode = document.querySelector('form'),
dataUrlResultNode = document.querySelector('#data-url-result'),
blobResultNode = document.querySelector('#blob-result');
function runBlobTests (filesArray) {
var promisesArray = [];
filesArray.forEach(function (file) {
var promise = new Promise(function (file, resolve, reject) {
var reader = new FileReader(),
startTime = Date.now();
reader.onload = function (resolve, startTime, e) {
var image = new Image(),
blob;
image.onload = function (resolve, startTime) {
URL.revokeObjectURL(this.src);
resolve(Date.now() - startTime);
}.bind(image, resolve, startTime);
blob = new Blob([e.target.result]);
image.src = URL.createObjectURL(blob);
}.bind(null, resolve, startTime);
reader.readAsArrayBuffer(file);
}.bind(null, file));
promisesArray.push(promise);
});
return Promise.all(promisesArray).then(function(values) {
var globalTestTime = 0;
values.forEach(function (value) {
globalTestTime += value;
});
blobResultNode.innerHTML = 'You browser spend ' + globalTestTime + ' ms for complete loading ' + values.length + ' images as a ArrayBuffer';
});
}
function runDataUrlTests (filesArray) {
var promisesArray = [];
filesArray.forEach(function (file) {
var promise = new Promise(function (file, resolve, reject) {
var reader = new FileReader(),
startTime = Date.now();
reader.onload = function (resolve, startTime, e) {
var image = new Image();
image.onload = function (resolve, startTime) {
URL.revokeObjectURL(this.src);
resolve(Date.now() - startTime);
}.bind(image, resolve, startTime);
image.src = e.target.result;
}.bind(null, resolve, startTime);
reader.readAsDataURL(file);
}.bind(null, file));
promisesArray.push(promise);
});
return Promise.all(promisesArray).then(function(values) {
var globalTestTime = 0;
values.forEach(function (value) {
globalTestTime += value;
});
dataUrlResultNode.innerHTML = 'You browser spend ' + globalTestTime + ' ms for complete loading ' + values.length + ' images as a DataUrl';
});
}
function runTests (files) {
var filesArray = [].slice.call(files);
if (!filesArray[0]) {
return alert("Please, select any files for tests...")
}
runDataUrlTests(filesArray).then(runBlobTests.bind(null, filesArray));
}
testFormNode.addEventListener('submit', function (e) {
e.preventDefault();
runTests(fileControl.files);
}, false);
}, false);
}());
@frontenddeveloping
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This gist compare FileReader.prototype.readAsArrayBuffer vs FileReader.prototype.readAsDataUrl - which is faster to read,create and load images from input[type="file"]. Because FileReader API is async, I use javascript native Promises (Chrome, Firefox support) to control and render test time.

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