Files
react-navigation/packages/stack/src/utils/memoize.tsx
2019-05-25 00:58:11 +02:00

34 lines
752 B
TypeScript

export default function memoize<Result, Deps extends ReadonlyArray<any>>(
callback: (...deps: Deps) => Result
) {
let previous: Deps | undefined;
let result: Result | undefined;
return (...dependencies: Deps): Result => {
let hasChanged = false;
if (previous) {
if (previous.length !== dependencies.length) {
hasChanged = true;
} else {
for (let i = 0; i < previous.length; i++) {
if (previous[i] !== dependencies[i]) {
hasChanged = true;
break;
}
}
}
} else {
hasChanged = true;
}
previous = dependencies;
if (hasChanged || result === undefined) {
result = callback(...dependencies);
}
return result;
};
}