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Optimize the sameMap function

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This commit is contained in:
Anders Hejlsberg
2018-01-16 12:51:46 -08:00
parent e96ec8c2c7
commit d52fa71f62
1 changed files with 9 additions and 11 deletions
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20
src/compiler/core.ts
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@@ -435,23 +435,21 @@ namespace ts {
export function sameMap<T>(array: T[], f: (x: T, i: number) => T): T[];
export function sameMap<T>(array: ReadonlyArray<T>, f: (x: T, i: number) => T): ReadonlyArray<T>;
export function sameMap<T>(array: T[], f: (x: T, i: number) => T): T[] {
let result: T[];
if (array) {
for (let i = 0; i < array.length; i++) {
if (result) {
result.push(f(array[i], i));
}
else {
const item = array[i];
const mapped = f(item, i);
if (item !== mapped) {
result = array.slice(0, i);
result.push(mapped);
const item = array[i];
const mapped = f(item, i);
if (item !== mapped) {
const result = array.slice(0, i);
result.push(mapped);
for (i++; i < array.length; i++) {
result.push(f(array[i], i));
}
return result;
}
}
}
return result || array;
return array;
}
/**