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Last active April 5, 2023 02:34
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Object (un)flattening in TypeScript
// Based on original implementation from Tofandel’s answer: https://stackoverflow.com/a/59787588/247441
/* Aggregates parts (mapped to slash-separated paths) into a nested object.
E.g.:
{ /some/path: A, /foo: B, /some/other/path: C }
gets turned into:
{ foo: B, some: { path: A, other: { path: C } } }
*/
export function unflattenObject<T extends Record<string, any>>
(parts: Record<string, any>): T {
const result: Record<string, any> = {};
// Ideally should be typed as Partial<T>, but that causes problems down the line
for (const partPath of Object.keys(parts)) {
if (Object.prototype.hasOwnProperty.call(parts, partPath)) {
const keys = partPath.match(/^\/+[^\/]*|[^\/]*\/+$|(?:\/{2,}|[^\/])+(?:\/+$)?/g);
if (keys) {
keys.reduce((accumulator, val, idx) => {
return accumulator[val] ?? (
(accumulator[val] = isNaN(Number(keys[idx + 1]))
? (keys.length - 1 === idx
? parts[partPath]
: {})
: [])
);
}, result);
}
}
}
return result as T;
}
/* Recursively decomposes an arbitrarily nested object into a flat record
of slash-separated part paths mapped to respective structures.
E.g.:
{ foo: B, some: { path: A, other: { path: C } } }
gets turned into:
{ /some/path: A, /foo: B, /some/other/path: C }
*/
export function flattenObject(
obj: Record<string, any>,
_prefix: false | string = false,
_result: Record<string, any> | null = null,
): Record<string, any> {
const result: Record<string, any> = _result ?? {};
// Preserve empty objects and arrays, they are lost otherwise
if (_prefix !== false &&
typeof obj === 'object' &&
obj !== null &&
Object.keys(obj).length === 0) {
result[_prefix] = Array.isArray(obj) ? [] : {};
return result;
}
const prefix = _prefix !== false
? (_prefix + path.posix.sep)
: path.posix.sep;
for (const i in obj) {
if (Object.prototype.hasOwnProperty.call(obj, i)) {
if (typeof obj[i] === 'object' && obj[i] !== null) {
// Recursion on deeper objects
flattenObject(obj[i], prefix + i, result);
} else {
result[prefix + i] = obj[i];
}
}
}
return result;
}
@tno2007
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tno2007 commented Apr 5, 2023

Cannot find name 'path' in flattenObject function

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