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refactor(compiler): replace flatten and map with flatMap. (#48378)

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Replace custom `flatten` and `map` with native `flatMap` usage.

Benchmark:
| Test case name 	| Result                                                 	|
|----------------	|--------------------------------------------------------	|
| flatten & map  	| flatten & map x 1,182 ops/sec ±2.18% (63 runs sampled) 	|
| flatMap        	| flatMap x 6,011 ops/sec ±0.91% (35 runs sampled)       	|

The fact that `flatMap` is faster is also highlighted in https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flatMap

PR Close #48378
This commit is contained in:
Alan Agius 2022-12-06 15:39:27 +00:00 committed by Andrew Kushnir
parent 11a24c3740
commit 146d2ee246
1 changed files with 3 additions and 9 deletions
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12
packages/compiler/src/render3/view/template.ts
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@ -1393,7 +1393,7 @@ export class TemplateDefinitionBuilder implements t.Visitor<void>, LocalResolver
return o.TYPED_NULL_EXPR;
}
const refsParam = flatten(references.map(reference => {
const refsParam = references.flatMap(reference => {
const slot = this.allocateDataSlot();
// Generate the update temporary.
const variableName = this._bindingScope.freshReferenceName();
@ -1410,8 +1410,9 @@ export class TemplateDefinitionBuilder implements t.Visitor<void>, LocalResolver
const refExpr = lhs.set(o.importExpr(R3.reference).callFn([o.literal(slot)]));
return nextContextStmt.concat(refExpr.toConstDecl());
}, true);
return [reference.name, reference.value];
}));
});
return asLiteral(refsParam);
}
@ -2360,10 +2361,3 @@ export interface ParsedTemplate {
*/
commentNodes?: t.Comment[];
}
function flatten<T>(list: Array<T|T[]>): T[] {
return list.reduce((flat: any[], item: T|T[]): T[] => {
const flatItem = Array.isArray(item) ? flatten(item) : item;
return (<T[]>flat).concat(flatItem);
}, []);
}