functional.js (λ)
functional.js is a functional JavaScript library. It facilitates currying and point-free / tacit programming.
Getting started
Using npm
npm install functional.js
To then include functional.min.js in your app:
var λ = require("functional.js");
Direct dependency
Download the minified version here, reference the js file and λ will become a global variable.
Using client side
There are possible issues with using the "λ" character client side. There shouldn't be, but there are. If you experience issues, there is an alternative client version, functional.min.client.js which uses "lambda" instead of "λ". Download the minified client version here, reference the js file and lambda will become a global variable.
Examples
Basic λ.curry example
var concatenate = λ.curry(function(word1, word2) {
return word1 + " " + word2;
});
var concatenateHello = concatenate("Hello");
var result = concatenateHello("World");
expect(result).toEqual("Hello World");
Another λ.curry example
var add = λ.curry(function(arg1, arg2, arg3) {
return arg1 + arg2 + arg3;
});
var add3 = add(3),
add5 = add3(2);
expect(add(3)(2)(1)).toEqual(6);
expect(add3(2, 1)).toEqual(6);
expect(add3(2)(1)).toEqual(6);
expect(add5(1)).toEqual(6);
Extending arity with λ.curry example
var add = λ.curry(function(arg1, arg2) {
return arg1 + arg2;
});
var add3 = add(3);
expect(add(1, 2, 3)).toEqual(6);
expect(add3(1, 2, 3, 4, 5)).toEqual(18);
Curried λ.each example
var result = [],
items = ["f", "u", "n", "c"];
var addTo = function (item) {
return result.push(item);
};
var addToResult = λ.each(addTo);
expect(typeof (addToResult)).toEqual("function");
addToResult(items);
expect(result).toEqual(["f", "u", "n", "c"]);
Curried λ.map example
var items = [1, 2, 3];
var doubleUp = function (number) {
return number * 2;
};
var doubleMap = λ.map(doubleUp);
expect(typeof (doubleMap)).toEqual("function");
var result = doubleMap(items);
expect(result).toEqual([2, 4, 6]);
Curried λ.reduce example
var items = [1, 2, 3];
var multiply = function (arg1, arg2) {
return arg1 * arg2;
};
var multiplyReduceFrom1 = λ.reduce(multiply, 1);
expect(typeof (multiplyReduceFrom1)).toEqual("function");
var result = multiplyReduceFrom1(items);
expect(result).toEqual(6);
Curried λ.any example
var items1 = [1, 2, 3],
items2 = [1, 3, 5];
var even = function (item) {
return item % 2 === 0;
};
var anyEven = λ.any(even);
expect(anyEven(items1)).toBeTruthy();
expect(anyEven(items2)).not.toBeTruthy();
Curried λ.select example
var items = [1, 2, 3, 4, 5];
var even = function (item) {
return item % 2 === 0;
};
var odd = function (item) {
return item % 2 !== 0;
};
var selectEven = λ.select(even);
var selectOdd = λ.select(odd);
expect(selectEven(items)).toEqual([2, 4]);
expect(selectOdd(items)).toEqual([1, 3, 5]);
Curried λ.first example
var items = [5, 4, 3, 2, 1];
var even = function (item) {
return item % 2 === 0;
};
var odd = function (item) {
return item % 2 !== 0;
};
var firstEven = λ.first(even);
var firstOdd = λ.first(odd);
expect(firstEven(items)).toEqual(2);
expect(firstOdd(items)).toEqual(1);
Curried λ.last example
var items = [5, 4, 3, 2, 1];
var even = function (item) {
return item % 2 === 0;
};
var odd = function (item) {
return item % 2 !== 0;
};
var lastEven = λ.last(even);
var lastOdd = λ.last(odd);
expect(lastEven(items)).toEqual(2);
expect(lastOdd(items)).toEqual(1);
Curried λ.every example
var items = [2, 4, 6, 8];
var even = function (item) {
return item % 2 === 0;
};
var odd = function (item) {
return item % 2 !== 0;
};
var everyEven = λ.every(even);
var everyOdd = λ.every(odd);
expect(everyEven(items)).toEqual(true);
expect(everyOdd(items)).toEqual(false);
Multiple λ.compose example
var e = function (a) {
return "hello " + a;
};
var f = function (a) {
return a + 1;
};
var g = function (a) {
return a * 100;
};
var composed = λ.compose(e, f, g);
expect(composed(2)).toEqual("hello 201");
Curried λ.partition example
var items = [7, 6, 5, 4, 3, 2, 1];
var even = function (item) {
return item % 2 === 0;
};
var partitionEven = λ.partition(even);
var result = partitionEven(items);
expect(result).toEqual([[6, 4, 2], [7, 5, 3, 1]]);
λ.toArray example (featuring λ.isArray)
var obj = {
"p1": "abc",
"p2": false,
"p3": null
};
var result = λ.toArray(obj);
expect(result).toEqual([["p1", "abc"], ["p2", false], ["p3", null]]);
expect(λ.isArray(obj)).toBeFalsy();
expect(λ.isArray(result)).toBeTruthy();
λ.apply example
var items = ["Hello", "World"];
var applyCase = λ.apply("toUpperCase");
var result = applyCase(items);
expect(result).toEqual(["HELLO", "WORLD"]);
λ.apply (multiple argument) example
var items = ["Hello", "World"];
var applyIndexOf = λ.apply(["substring", "1", "4"]);
var result = applyIndexOf(items);
expect(result).toEqual(["ell", "orl"]);
Basic λ.assign (λ.extend) example
var obj1 = {
prop1: "obj1prop1",
prop2: "obj1prop2"
};
var obj2 = {
prop2: "obj2prop2",
prop3: "obj2prop3"
};
var result = λ.assign(obj1, obj2);
expect(result).toEqual({
prop1: "obj1prop1",
prop2: "obj1prop2",
prop3: "obj2prop3"
});
Extend λ.assign arity with λ.curry example
var obj1 = {
prop1: "obj1prop1",
prop2: "obj1prop2"
};
var obj2 = {
prop2: "obj2prop2",
prop3: "obj2prop3",
prop4: "obj2prop4"
};
var obj3 = {
prop4: "obj3prop4",
prop5: "obj3prop5"
};
var assignToObj1 = λ.assign(obj1);
var result1 = assignToObj1(obj2, obj3);
var result2 = λ.assign(obj1, obj2, obj3);
expect(result1).toEqual({
prop1: "obj1prop1",
prop2: "obj1prop2",
prop3: "obj2prop3",
prop4: "obj2prop4",
prop5: "obj3prop5"
});
expect(result1).toEqual(result2);
License
MIT License