JavaScript often deals with converting an array of objects into an object of arrays, but how would you accomplish this in TypeScript while maintaining full typing support?
JavaScript often deals with converting an array of objects into an object of arrays, but how would you accomplish this in TypeScript while maintaining full typing support?
interface Pivot<T> {
[K in keyof T]: T[K][];
}
function createPivot<T extends Record<any, any>>(items: T[]): Pivot<T> {
return Object.keys(items[0]).reduce((obj, key) => {
obj[key] = items.map(item => item[key]);
return obj;
}, {} as Pivot<T>);
}
If the function createPivot doesn't work at run-time, please provide example inputs and outputs. If additional "typing support" is needed, please add examples that should be rejected and accepted at compile-time.
Follow this method
**
* Change an array of non-nested objects into an object of arrays.
* Assumes all objects have the same structure.
* */
type IndexObject = { [index: string]: any }; // not the best solution, but works for now :(
function reorganize<T>(arr: (T & IndexObject)[]) {
type Subset = { [K in keyof T]?: T[K] }; // make it optional to construct the new object
let result: IndexObject & Subset = {};
Object.keys(arr[0]).forEach(k => {
result[k] = arr.map(obj => obj[k]);
});
return result as { [K in keyof T]: T[K] }; // remove the optionality of every key
}
If you have better suggestions, feel free to share them
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