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docs(ivy): document rules for the global state access (#30485) 

PR Close #30485
This commit is contained in:
Pawel Kozlowski 2019-05-15 16:13:59 +02:00 committed by Jason Aden
parent b4014e9a39
commit 07ebe9624f
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14
packages/core/src/render3/PERF_NOTES.md
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@ -104,8 +104,18 @@ export function i18nStartFirstTemplatePass(tView: TView, index: number, message:
}
```
## Loops
Don't use `forEach`, it can cause megamorphic function calls (depending on the browser) and function allocations.
It is [a lot slower than regular `for` loops](https://jsperf.com/for-vs-foreach-misko)
## Limit global state access
Ivy implementation uses some variables in `packages/core/src/render3/state.ts` that could be considered "global state" (those are not truly global variables exposed on `window` but still those variables are easily accessible from anywhere in the ivy codebase). Usage of this global state should be limited to avoid unnecessary function calls (state getters) and improve code readability.
As a rule, the global state should be accessed _only_ from instructions (functions invoked from the generated code).
## Instructions should be only called from the generated code
Instruction functions should be called only from the generated template code. As a consequence of this rule, instructions shouldn't call other instructions.
Calling instructions from other instructions (or any part of the ivy codebase) multiplies global state access (see previous rule) and makes reasoning about code more difficult.