I am creating a web application that uses EvaporateJS to upload large files to Amazon S3 using Multipart Uploads. I noticed a problem when every time a new piece was launched, the browser froze for ~ 2 seconds. I want the user to be able to continue using my application while loading, and this freezing makes this a bad experience.
I used Chrome’s chronology to examine what caused this, and found that it was SparkMD5 hashing. So I moved the entire boot process to Work, which I thought would fix the problem.
Ok, the issue is now fixed in Edge and Firefox, but Chrome still has the same issue.
Here is a screenshot of my timeline:

, , < 8ms JavaScript. Worker, ~ 600 , 1386 , .
, , - , ?
:
var window = self;
var document = {
createElement: function() {
var href = undefined;
var elm = {
set href(url) {
var obj = new URL(url);
elm.protocol = obj.protocol;
elm.hostname = obj.hostname;
elm.pathname = obj.pathname;
elm.port = obj.port;
elm.search = obj.search;
elm.hash = obj.hash;
elm.host = obj.host;
href = url;
},
get href() {
return href;
},
protocol: undefined,
hostname: undefined,
pathname: undefined,
port: undefined,
search: undefined,
hash: undefined,
host: undefined
};
return elm;
}
};
importScripts("/lib/sha256/sha256.min.js");
importScripts("/lib/spark-md5/spark-md5.min.js");
importScripts("/lib/url-parse/url-parse.js");
importScripts("/lib/xmldom/xmldom.js");
importScripts("/lib/evaporate/evaporate.js");
DOMParser = self.xmldom.DOMParser;
var defaultConfig = {
computeContentMd5: true,
cryptoMd5Method: function (data) { return btoa(SparkMD5.ArrayBuffer.hash(data, true)); },
cryptoHexEncodedHash256: sha256,
awsSignatureVersion: "4",
awsRegion: undefined,
aws_url: "https://s3-ap-southeast-2.amazonaws.com",
aws_key: undefined,
customAuthMethod: function(signParams, signHeaders, stringToSign, timestamp, awsRequest) {
return new Promise(function(resolve, reject) {
var signingRequestId = currentSigningRequestId++;
postMessage(["signingRequest", signingRequestId, signParams.videoId, timestamp, awsRequest.signer.canonicalRequest()]);
queuedSigningRequests[signingRequestId] = function(signature) {
queuedSigningRequests[signingRequestId] = undefined;
if(signature) {
resolve(signature);
} else {
reject();
}
}
});
},
bucket: undefined,
allowS3ExistenceOptimization: false,
maxConcurrentParts: 5
}
var currentSigningRequestId = 0;
var queuedSigningRequests = [];
var e = undefined;
var filekey = undefined;
onmessage = function(e) {
var messageType = e.data[0];
switch(messageType) {
case "init":
var globalConfig = {};
for(var k in defaultConfig) {
globalConfig[k] = defaultConfig[k];
}
for(var k in e.data[1]) {
globalConfig[k] = e.data[1][k];
}
var uploadConfig = e.data[2];
Evaporate.create(globalConfig).then(function(evaporate) {
var e = evaporate;
filekey = globalConfig.bucket + "/" + uploadConfig.name;
uploadConfig.progress = function(p, stats) {
postMessage(["progress", p, stats]);
};
uploadConfig.complete = function(xhr, awsObjectKey, stats) {
postMessage(["complete", xhr, awsObjectKey, stats]);
}
uploadConfig.info = function(msg) {
postMessage(["info", msg]);
}
uploadConfig.warn = function(msg) {
postMessage(["warn", msg]);
}
uploadConfig.error = function(msg) {
postMessage(["error", msg]);
}
e.add(uploadConfig);
});
break;
case "pause":
e.pause(filekey);
break;
case "resume":
e.resume(filekey);
break;
case "cancel":
e.cancel(filekey);
break;
case "signature":
var signingRequestId = e.data[1];
var signature = e.data[2];
queuedSigningRequests[signingRequestId](signature);
break;
}
}
, , AWS, Buks Bucket AWS Region, AWS Object Key File, "init". - , "" , , , "" , API.