TStools

Zero-dependency and lightweight library with TypeScript utilities.

Installation

npm

npm i @stnekroman/tstools

yarn

yarn add @stnekroman/tstools

Types.ts

Set of pure TypeScript utility types.

Arrays.ts

Helper methods for operations with arrays.

Objects.ts

Helper methods for operations with objects and different values.

Throttle.ts

Implementations of throttle patten (aka debounce)

Functions.ts

Types for functions for better readability with some utilities.
Highlights:

• Functions.memo caching/"memoization" of passed function
• Functions.pipe piping/chaining of functions

Cache.ts

Promise-based implemetation of caching.
Examples of usage:

• SimpleCache.ts
• TwoKeyCache.ts
• ObjectArgCache.ts
• ObjectKeyCache.ts

ThrottledCache.ts

Combination of Cache + Throttle patterns.
Examples of usage:

• SimpleThrottledCache.ts
• BulkThrottledCache.ts

Decorators:

• Implements — like built-in overrides keyword, but for ensuring, that method/prop implements one of class'es interface
• SingletonGuard — ensures that class can have only not more than 1 instance. (new invoked only 0 or 1 times)

Optional.ts

Java-port of old good Optional monad.
Usage:

const value = Optional.of(2)
                      .map(value => value*value)
                      .filter(value => value === 3)
                      .orElse(0);

Sorter.ts

Sorter (comparator) builder - by fieldname or by custom extractor.
Examples of usage:

const data : Item[] = [
  {a: 1, b: 1},
  {a: 2, b: 1},
  {a: 2, b: 2}
];

// sort by one field
arr.sort(Sorter.byField("a").build());

// sort by two fields - initially by "a", later - by "b"
data.sort(Sorter.byField<Item>("a").build(
  Sorter.byField("b").inverse().build()
));

// by extractor
arr.sort(Sorter.byExtractor<Item>(item => item.c).build());

Look for more in Sorter.test.ts

GroupBy.ts

GroupBy builder - by fieldname or by extractor to object or map.
Analog of ES15's Object.groupBy, Map.groupBy but with next differences:

1. Supports inner transform of data during grouping.
   So while built-in groupBy preserves original items, just groups them to array, - this groupby can (optionally) collect different objects to group arrays.
   For example, you may want to drop field, which was used for grouping.
2. Built-in approach doesn't support stream processing of data - it expects, that you already have ready-to-use array of input items.
   While this groupBy accepts each item individually and updates resulting accumulator with grouped data automatically on fly.
3. Build-in approach groups only top-level, while ini real life you will face many situations, where you need sub-grouping.
   Of course, you can post-process result of Object.groupBy and group nested groups, but that will mean mode code and additional pass (watch performance)

Examples of usage:

// sample data
const data : TestItemABC[] = [
    {a: 1, b: 1, c: 1},
    {a: 1, b: 1, c: 2},
    {a: 2, b: 1, c: 3},
    {a: 2, b: 2, c: 1},
    {a: 2, b: 2, c: 2},
    {a: 3, b: 2, c: 3},
    {a: 3, b: 3, c: 1}
  ];

// shortcut usage
GroupBy(data).toMap("a");

// result is:
{
  "1" : [{a: 1, b: 1, c: 1}, {a: 1, b: 1, c: 2}],
  "2" : [{a: 2, b: 1, c: 3}, {a: 2, b: 2, c: 1}, {a: 2, b: 2, c: 2}],
  "3" : [{a: 3, b: 2, c: 3}, {a: 3, b: 3, c: 1}]
};

// Fully-qualified usasge:
const acc : GroupBy.ObjectGroupByAccumulator<...> = GroupBy.toObject<TestItemABC>()
                                                           .byExtractor(i => i.a)
                                                           .valueExtractor(i => ({b: i.b, c: i.c}))
                                                           .build();
acc.consume(data[0]);
acc.result; // accumulator's result will contain ready-to-use structure after each consume/insert
acc.consume(data[1]);
acc.result;
acc.consume(data[2]);
...

// With nested grouping
const acc = GroupBy.toObject<TestItemABC>()
                   .byField("a")
                   .valueExtractor(i => ({b: i.b, c: i.c} as TestItemBC))
                   .build( // pass nested grouper
                      () => GroupBy.toObject<TestItemBC>()
                                   .byField("b")
                                   .valueExtractor(i => ({c: i.c} as TestItemC))
                                   .build()
                   );
acc.consumeAll(data);

acc.result; // will contain:

{
  "1" : {
    "1": [{c: 1}, {c: 2}]
  },
  "2" : {
    "1": [{c: 3}],
    "2": [{c: 1}, {c: 2}]
  },
  "3": {
    "2": [{c: 3}],
    "3": [{c: 1}]
  }
}

Fully-qualified version returns instance of GroupBy.Accumulator<T, R> which can be used to collect inputs and build the result.
It has next methods:

• consume(data : T) : this — consumes one individual sample of data
• consumeAll(datas : T[]) : this — consumes array of data
• get result() : Types.DeepReadonly<R> — reference to container, which contains grouped results
• clear() : void — clears this accumulator

Look for more in ObjectGroupBy.test.ts or MapGroupBy.test.ts

License MIT