Improved looping; safely mutate listeners queue #63
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crazy4groovy
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package.json
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| @@ -89,7 +90,7 @@ | |||
| "eslint-config-developit": "^1.1.1", | |||
| "gzip-size-cli": "^2.1.0", | |||
| "jest": "^21.2.1", | |||
| "microbundle": "^0.2.4", | |||
| "microbundle": "^0.3.1", | |||
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Needed update to work on Windows
src/index.js
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| } | ||
| listeners = out; | ||
| const i = listeners.indexOf(listener); | ||
| if (i > -1) listeners.splice(i, 1); |
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This shifts the indices within the Array during event firing, which can cause the wrong set of listeners to be invoked.
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The listeners are called in descending order, so I think the shifted index is irrelevant - the others before it will still be called.
src/util.js
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| for (let i in props) obj[i] = props[i]; | ||
| return obj; | ||
| // Lighter Object.assign clone | ||
| export function assign(_) { |
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This is expensive: now assign() has variable arity and is unlikely to be optimized.
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It saves bytes compared to its uses.
Also, I'm pretty sure that this is a safe use for optimizations. See https://github.com/petkaantonov/bluebird/wiki/Optimization-killers#what-is-safe-arguments-usage
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On this note, why not just use Object.assign? Support is extremely good: http://kangax.github.io/compat-table/es6/#test-Object_static_methods
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how are you checking the byte savings? we only care about gzipped output size, not the source size. Unistore supports IE9+ so Object.assign isn't available.
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Would you "object" (pun intended) to documenting a need for a polyfill for older (IE <= 11) browser support? Could rip this out altogether.
If not:
I based my saved bytes comment off the fact that assign doesn't need multiple invocations for combining multiple objects, as is its use case in the code. I could test which net-size is smaller between the two ways.
src/index.js
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| } | ||
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| function setState(update, overwrite, action) { | ||
| state = overwrite ? update : assign(assign({}, state), update); | ||
| let currentListeners = listeners; |
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Remove this means that a subscribed function that unsubcribes itself will cause the next listener to be skipped.
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Are you attempting to hedge the case where a listener cb unsubscribes itself, thus modifies the listeners array? I can see your point now. I may write a test case to prove your example.
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Does the new test satisfy your concern now?
src/index.js
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| for (let i=0; i<arguments.length; i++) args.push(arguments[i]); | ||
| let ret = action.apply(this, args); | ||
| const args = [state]; | ||
| const l = arguments.length; |
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Hoisting this adds bytes and can actually hurt performance.
mraleph has a great blog post describing the effect in detail here:
http://mrale.ph/blog/2014/12/24/array-length-caching.html
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I'll agree with these points.
| let out = []; | ||
| for (let i=0; i<listeners.length; i++) { | ||
| if (listeners[i]===listener) { | ||
| listener = null; |
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Looking at this, I'm not sure what value is added by setting listener to null here. Wouldn't listener just fall out of scope and be gc'ed anyway?
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Setting listener to null prevents the removal of any additional listeners in that loop.
test/unistore.test.js
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| expect(sub1).toHaveBeenCalledTimes(2); | ||
| expect(sub2).toHaveBeenCalledTimes(1); | ||
| expect(sub3).toHaveBeenCalledTimes(2); | ||
| expect(called).toEqual([3, 2, 1, 3, 1]); |
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I may be testing too much here IMO. Maybe use a sort() or something, just to check calls and not the order they were called.
crazy4groovy
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package.json
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| @@ -28,15 +29,15 @@ | |||
| "bundlesize": [ | |||
| { | |||
| "path": "full/preact.js", | |||
| "maxSize": "750b" | |||
| "maxSize": "727b" | |||
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the other assign function cost an additional 17 bytes, so we should keep the existing one - good call!
crazy4groovy
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…ners unsubscribing
Admittedly I can't run the tests on my Windows machine :(
So take this PR with a grain of salt.
Error: ENOENT: no such file or directory, open 'D:\dev\projects\unistore\src\integrations*.js'
Error: ENOENT: no such file or directory, open 'D:\dev\projects\unistore\src\combined*.js'
Build output to dist:
554 B: unistore.es.js
323 B: unistore.js
391 B: unistore.umd.js
325 B
ERROR There is no matching file for full/preact.js in D:\dev\projects\unistore
Cheers