137 lines
3.2 KiB
Markdown
137 lines
3.2 KiB
Markdown
tk-functional
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=============
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[](https://gitlab.com/thunderk/tk-functional/commits/master)
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[](https://gitlab.com/thunderk/tk-functional/commits/master)
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[](https://npmjs.com/tk-functional)
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[](https://bundlephobia.com/result?p=tk-functional)
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About
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-----
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Provides some common helpers for functional-style programming.
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Typescript definitions are included.
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Issues can be reported on [GitLab](https://gitlab.com/thunderk/tk-functional/issues).
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Functions
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---------
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**always** and **never** return true and false respectively
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```typescript
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always() // => true
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never() // => false
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```
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**and** and **or** combines predicates
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```typescript
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const a = and((x: number) => x > 2, (x: number) => x < 5);
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a(2) // => false
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a(3) // => true
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a(4) // => true
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a(5) // => false
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const o = or((x: number) => x < 2, (x: number) => x > 3);
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o(1) // => true
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o(2) // => false
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o(3) // => false
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o(4) // => true
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```
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**attr** gets an object's attribute:
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```typescript
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const getx = attr("x");
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getx({x: 3}); // => 3
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```
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**bool** checks for boolean equivalence (in a broader sense than !(!(val))):
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```typescript
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bool(undefined); // => false
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bool(null); // => false
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bool(-1); // => true
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bool(0); // => false
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bool(1); // => true
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bool(""); // => false
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bool(" "); // => true
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bool("abc"); // => true
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bool([]); // => false
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bool([1, 2, 3]); // => true
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bool({}); // => false
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bool({x: 1}); // => true
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```
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**cmp** simplifies the use of array sorting:
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```typescript
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[8, 3, 5].sort(cmp()) // => [3, 5, 8]
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[8, 3, 5].sort(cmp({ reverse: true })) // => [8, 5, 3]
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[-2, 8, -7].sort(cmp({ key: Math.abs })) // => [-2, -7, 8]
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```
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**identity** returns its argument untouched:
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```typescript
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a === identity(a) // => true
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```
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**is** and **isinstance** checks for strict equality and inheritance:
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```typescript
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const f = is(8);
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f(8) // => true
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f(5 + 3) // => true
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f("8") // => false
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f(null) // => false
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class A { }
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class A1 extends A { }
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class A2 extends A { }
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class B { }
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const f: any[] = [5, null, undefined, new A, new A1, new B, new A2];
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const result: A[] = f.filter(isinstance(A)); // => [f[3], f[4], f[6]]
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```
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**nn**, **nu** and **nnu** checks at run-time for null or undefined:
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```typescript
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nn(undefined) // => undefined
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nn(null) // => Error
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nn(1) // => 1
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nu(undefined) // => Error
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nu(null) // => null
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nu(1) // => 1
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nnu(undefined) // => Error
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nnu(null) // => Error
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nnu(1) // => 1
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```
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**nop** does nothing (useful for some callbacks):
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```typescript
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new ConstructorWithMandatoryCallback(nop)
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```
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**partial** applies a partial configuration object as first argument of compatible functions:
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```typescript
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const sum = (args: {a: number, b: number}) => args.a + args.b
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const plus1 = partial({a: 1}, sum);
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plus1({b: 8}) // => 9
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```
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**pipe** chains two functions as one:
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```typescript
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const f = pipe((x: number) => x * 2, (x: number) => x + 1);
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f(3) // => 7 ((3 * 2) + 1)
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```
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