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Sammons/helpers-ts-2.ts

Created November 6, 2018 04:10
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helpers-ts-2.ts
function AtPath<Target extends {}, Path1 extends keyof Target>(target: Target, path1: Path1): Target[Path1]
function AtPath<Target extends {}, Path1 extends keyof Target, Path2 extends keyof Target[Path1]>(target: Target, path1: Path1, path2: Path2): Target[Path1][Path2]
function AtPath<Target extends {}, Path1 extends keyof Target, Path2 extends keyof Target[Path1], Path3 extends keyof Target[Path1][Path2]>(target: Target, path1: Path1, path2: Path2, path3: Path3): Target[Path1][Path2][Path3]
function AtPath(target: {}, ...paths: string[]) {
let result = target as any;
for (let path of paths) {
result = result[path];
if (result === void 0) {
return result;
}
}
return result;
}
// result is "blue", if we access a path that does not exist, it does not compile
const result = AtPath({ color: colors.blue }, 'color');
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