A new feature I would like to suggest is a universal groupBy() function that facilitates grouping a collection based on a specific key.
function groupBy(iterable, fn) {
const groups = new Map();
for (const item of iterable) {
const key = fn(item);
if (!groups.has(key)) groups.set(key, []);
groups.get(key).push(item);
}
return groups;
}
Using this function allows us to categorize data by:
const groups = groupBy(input_array, item => JSON.stringify([item.name, item.day]));
The choice to use JSON.stringify() is deliberate as two arrays are considered equal only if they reference the same array. Thus, creating a new array instance like [item.name, item.day] will never match an existing key. Serializing the array using JSON allows comparison between strings instead, making the process feasible.
// normal array comparison
["alagu", "monday"] === ["alagu", "monday"] //=> false
// serialized (using JSON) array comparison
'["alagu","monday"]' === '["alagu","monday"]' //=> true
Once the data is grouped, the structure of groups appears as follows:
// displaying Map instance contents in object notation
Map{
'["alagu","monday"]': [
{ name: "alagu", day: "monday", time: "morning", task: "studying" },
{ name: "alagu", day: "monday", time: "evening", task: "playing" },
{ name: "alagu", day: "monday", time: "night" , task: "sleeping" },
],
'["alagu","sunday"]': [
{ name: "alagu", day: "sunday", time: "morning", task: "playing" },
{ name: "alagu", day: "sunday", time: "evening", task: "playing" },
{ name: "alagu", day: "sunday", time: "night" , task: "sleeping" },
],
}
To convert this into an array, we can utilize Array.from(groups) and provide custom transformations through map().
const result_array = Array.from(groups).map(([json, items]) => {
const [name, day] = JSON.parse(json);
const schedule = items.map(({ time, task }) => ({ time, task }));
return { name, day, schedule };
});
In the above implementation, the serialized key is decoded back into its original JavaScript form using JSON.parse(), enabling retrieval of the name and day values of each group.
The next step involves transforming items, an array containing all properties, into objects with only time and task attributes.
.map(({ time, task }) => ({ time, task }))
achieves this goal efficiently, combining object destructuring with property shorthand syntax.