Improve better performance

[xqdoo00o]

Use larger chunkSize(64K) increase generateasync perf。
And use a robust setimmediate polyfill could increase generateasync perf of the zip with lots of chunks (min.js just 1KB larger ).
(Current setImmediate polyfill (after v3.15) using setTimeout(fn, 0) cause 4ms+ delay(browser) or 1ms delay(node.js) each chunk (current 16K size), see perf demo).

Test result for a zip with 16 files(chunks):
before:
store: 200ms
after:
store: 30ms

This PR may resolve the issue #617.

[101arrowz]

@Stuk updates on this? There's a massive difference in performance between 3.1.5 and 3.5.0.

[fpaupier]

Still having this issue with the proposed workaround. Any tips?

[101arrowz]

I'd recommend switching to a different library, at least until this is merged. zip.js and fflate (my own library) are solid alternatives.

[Stuk]

Could you merge master into this branch so that the unit tests will run? Thanks!

[xqdoo00o]

Could you merge master into this branch so that the unit tests will run? Thanks!

Thanks, I merged.

[mark-westerhof]

Can this merge now?

[iiLearner]

is this being worked on anymore?

[AlttiRi]

What do you waiting for? @Stuk

set-immediate-shim is unacceptably slow.
The existence of this lib is a joke, it only provides setTimeout with "setImmediate" name. The absolutely useless "library".

Or setimmediate (of this pull request) is too big for you?

---

Since delay uses only the callback param of setImmediate

jszip/lib/utils.js

Lines 404 to 408 in 38f8373

	exports.delay = function(callback, args, self) {
	setImmediate(function () {
	callback.apply(self || null, args || []);
	});
	};

...just use the follow code instead of importing a library:

const setImmediate = globalThis.setImmediate || /*#__PURE__*/ (function() {
    const {port1, port2} = new MessageChannel();
    const queue = [];
    port1.onmessage = function() {
        const callback = queue.shift();
        callback();
    };
    return function setImmediateLike(callback) { // Simplified implementation: only callback argument.
        port2.postMessage(null);
        queue.push(callback);
    };
})();

The implementation of setImmediate based on MessageChannel is supported everywhere:
https://developer.mozilla.org/en-US/docs/Web/API/MessageChannel#browser_compatibility
https://caniuse.com/mdn-api_messagechannel_messagechannel

---

ES5 version to pass linter:

var setImmediate = typeof setImmediate === "function" ? setImmediate : /*#__PURE__*/ (function() {
    var channel = new MessageChannel();
    var port1 = channel.port1;
    var port2 = channel.port2;
    var queue = [];
    port1.onmessage = function() {
        var callback = queue.shift();
        callback();
    };
    return function setImmediateLike(callback) { // Simplified implementation: only callback argument.
        port2.postMessage(null);
        queue.push(callback);
    };
})();

Just put it before 404 line (also remove the import and the dependency):

jszip/lib/utils.js

Line 404 in 38f8373

exports.delay = function(callback, args, self) {

All tests are passed. Works properly. And fast (as expected).

# pass 186
...
chromium { passed: 3301, failed: 0, total: 3301, runtime: 8940, tests: [] }
firefox { passed: 3301, failed: 0, total: 3301, runtime: 8585, tests: [] }
webkit { passed: 3301, failed: 0, total: 3301, runtime: 8367, tests: [] }