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A set of pure ES2015 functions aimed to make functional JavaScript more idiomatic.
// Examples at https://gist.github.com/bendc/9b05735dfa6966859025#gistcomment-1370485
// array utils
// =================================================================================================
const combine = (...arrays) => [].concat(...arrays);
const compact = arr => arr.filter(Boolean);
const contains = (() => Array.prototype.includes
? (arr, value) => arr.includes(value)
: (arr, value) => arr.some(el => el === value)
)();
const difference = (arr, ...others) => {
var combined = [].concat(...others)
return arr.filter(el => !combined.some(exclude => el === exclude))
};
const head = arr => arr[0];
const initial = arr => arr.slice(0, -1);
const intersection = (...arrays) =>
[...Set([].concat(...arrays))].filter(toFind =>
arrays.every(arr => arr.some(el => el === toFind))
);
const last = arr => arr.slice(-1)[0];
const sortedIndex = (arr, value) =>
[value].concat(arr).sort().indexOf(value);
const tail = arr => arr.slice(1);
const toArray = (() => Array.from ? Array.from : obj => [].slice.call(obj))();
const union = (...arrays) => [...Set([].concat(...arrays))];
const unique = arr => [...Set(arr)];
const without = (arr, ...values) =>
arr.filter(el => !values.some(exclude => el === exclude));
// object utils
// =================================================================================================
const getValues = obj => Object.keys(obj).map(key => obj[key]);
const merge = (() => {
const extend = Object.assign ? Object.assign : (target, ...sources) => {
sources.forEach(source =>
Object.keys(source).forEach(prop => target[prop] = source[prop])
);
return target;
};
return (...objects) => extend({}, ...objects);
})();
const toMap = (() => {
const convert = obj => new Map(Object.keys(obj).map(key => [key, obj[key]]));
return obj => obj instanceof Map ? obj : convert(obj);
})();
// math
// =================================================================================================
const min = arr => Math.min(...arr);
const max = arr => Math.max(...arr);
const sum = arr => arr.reduce((a, b) => a + b);
const product = arr => arr.reduce((a, b) => a * b);
// function decorators
// =================================================================================================
const not = fn => (...args) => !fn(...args);
const maybe = fn =>
(...args) => {
if (args.length < fn.length || args.some(arg => arg == null)) return;
return fn(...args);
};
const once = fn => {
var done = false;
return (...args) => {
if (done) return;
done = true;
fn(...args);
};
};
const curry = fn => {
const arity = fn.length;
const curried = (...args) =>
args.length < arity ? (...more) => curried(...args, ...more) : fn(...args);
return curried;
};
const pipeline = (...funcs) =>
value => funcs.reduce((a, b) => b(a), value);
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