@ayc0/std

Standard

Import

To install, run either npm install --save @ayc0/std or yarn add @ayc0/std, and then:

const std = require('@ayc0/std');
const multiplyBy2 = std.map(x => x * 2);

// OR

const map = require('@ayc0/std/map');
const multiplyBy2 = map(x => x * 2);

// And then you can use it:

const input = [1, 2];
const output = multiplyBy2(input);

Supported functions

For all of the functions listed below, you can either do std.<function> or import them from @ayc0/std/<function>:

• range
• zip
• len
• map
• forEach
• filter
• reduce
• take
• drop
• find
• every
• some
• Iterable

Range

function* range([from,] to[, step]) {
  // yield every steps
}

Zip

function* zip(iterables) {
  // yield [currentValues, indexes, iterables]
}

Supported iterables

• array
• string
• Map
• Set
• Object
• iterators

Examples

for (const [currentValues, indexes, iterables] of zip([
  '123',
  [1, 2, 3],
  { a: 1, b: 2, c: 3 },
])) {
  console.log(currentValues);
  // [ '1', 1, 1 ]
  // [ '2', 2, 2 ]
  // [ '3', 3, 3 ]
  console.log(indexes);
  // [ 0, 0, 'a' ]
  // [ 1, 1, 'b' ]
  // [ 2, 2, 'c' ]
}

Len

function len(iterable) {
  // return length of iterable
}

Supported iterables

• array
• string
• Map
• Set
• Object
• iterators

Map

function map(callback[, thisArg]) {
  return function (iterable) {
    // return new iterable of the input iterable type
  }
}

function callback(currentValue[, index[, iterable]]) {
  // return new element of iterable
}

Supported iterables

• array
• string
• Map
• Set
• Object
• iterators

Examples

map(x => x * 2)({ a: 1, b: 2 });
// { a: 2, b: 4 }
map(x => x * 2)([1, 2]);
// [ 2, 4 ]
map(x => x * 2)(new Set([1, 2]));
// Set(2) {2, 4}
map(x => x * 2)(
  new Map([
    ['a', 1],
    ['b', 2],
  ]),
);
// Map(2) {"a" => 2, "b" => 4}
map(x => x.repeat(2))('ab');
// 'aabb'

ForEach

function forEach(callback[, thisArg]) {
  return function (iterable) {
  }
}

function callback(currentValue[, index[, iterable]]) {
}

Supported iterables

• array
• string
• Map
• Set
• Object
• iterators

Examples

forEach(x => console.log(x * 2))({ a: 1, b: 2 });
// 2
// 4
forEach(x => console.log(x * 2))([1, 2]);
// 2
// 4
forEach(x => console.log(x * 2))(new Set([1, 2]));
// 2
// 4
forEach(x => console.log(x * 2))(
  new Map([
    ['a', 1],
    ['b', 2],
  ]),
);
// 2
// 4
forEach(x => console.log(x.repeat(2)))('ab');
// aa
// bb

Filter

function filter(callback[, thisArg]) {
  return function (iterable) {
    // return new iterable of the input iterable type
  }
}

function callback(currentValue[, index[, iterable]]) {
  // return if you should keep this element of not
}

Supported iterables

• array
• string
• Map
• Set
• Object
• iterators

Examples

filter(x => x % 2)({ a: 1, b: 2 });
// { a: 1 }
filter(x => x % 2)([1, 2]);
// [ 1 ]
filter(x => x % 2)(new Set([1, 2]));
// Set(1) {1}
filter(x => x % 2)(
  new Map([
    ['a', 1],
    ['b', 2],
  ]),
);
// Map(1) {"a" => 1}
filter(x => x % 2)('12');
// '1'

Reduce

function reduce(callback, initialValue, thisArg) {
  return function (iterable) {
    // return reduced value
  };
}

function callback(accumulator, currentValue[, index[, iterable]]) {
  // returns the value that results from the reduction
}

Supported iterables

• array
• string
• Map
• Set
• Object
• iterators

Examples

reduce((acc, x) => acc + x, 0)({ a: 1, b: 2 });
// { a: 1 }
reduce((acc, x) => acc + x, 0)([1, 2]);
// [ 1 ]
reduce((acc, x) => acc + x, 0)(new Set([1, 2]));
// Set(1) {1}
reduce(
  (acc, x) => acc + x,
  0,
)(
  new Map([
    ['a', 1],
    ['b', 2],
  ]),
);
// Map(1) {"a" => 1}
reduce((acc, x) => acc + Number(x), 0)('12');
// '1'

Take

function take(limit) {
  return function (iterable) {
    // return new iterable with only the <limit> first items
  };
}

Supported iterables

• array
• string
• Map
• Set
• Object
• iterators

Examples

take(1)({ a: 1, b: 2 });
// { a: 1 }
take(1)([1, 2]);
// [ 1 ]
take(1)(new Set([1, 2]));
// Set(1) {1}
take(1)(
  new Map([
    ['a', 1],
    ['b', 2],
  ]),
);
// Map(1) {"a" => 1}
take(1)('ab');
// 'a'

Drop

function drop(limit) {
  return function (iterable) {
    // return new iterable with <limit> first item trimmed
  };
}

Supported iterables

• array
• string
• Map
• Set
• Object
• iterators

Examples

drop(1)({ a: 1, b: 2 });
// { b: 2 }
drop(1)([1, 2]);
// [ 2 ]
drop(1)(new Set([1, 2]));
// Set(1) {2}
drop(1)(
  new Map([
    ['a', 1],
    ['b', 2],
  ]),
);
// Map(1) {"b" => 2}
drop(1)('ab');
// 'b'

Find

function find(callback[, thisArg]) {
  return function (iterable) {
    // return the element and its key or undefined
  }
}

function callback(currentValue[, index[, iterable]]) {
  // return if you it matches your element or not
}

Supported iterables

• array
• string
• Map
• Set
• Object
• iterators

Examples

find(x => x % 2)({ a: 1, b: 2 });
// [ 1, 'a' ]
find(x => x % 2)([1, 2]);
// [ 1, 0 ]
find(x => x % 2)(new Set([1, 2]));
// [ 1, 0 ]
find(x => x % 2)(
  new Map([
    ['a', 1],
    ['b', 2],
  ]),
);
// [ 1, 'a' ]
find(x => x % 2)('12');
// [ '1', 0 ]

Every

function every(callback[, thisArg]) {
  return function (iterable) {
    // return true if all elements match the callback
  }
}

function callback(currentValue[, index[, iterable]]) {
  // return if you it matches your element or not
}

Supported iterables

• array
• string
• Map
• Set
• Object
• iterators

Examples

every(x => x <= 2)({ a: 1, b: 2 });
// true
every(x => x <= 2)([1, 2]);
// true
every(x => x <= 2)(new Set([1, 2]));
// true
every(x => x <= 2)(
  new Map([
    ['a', 1],
    ['b', 2],
  ]),
);
// true
every(x => x === '1')('12');
// false

Some

function some(callback[, thisArg]) {
  return function (iterable) {
    // return true if at least 1 element matches the callback
  }
}

function callback(currentValue[, index[, iterable]]) {
  // return if you it matches your element or not
}

Supported iterables

• array
• string
• Map
• Set
• Object
• iterators

Examples

some(x => x <= 2)({ a: 1, b: 2 });
// true
some(x => x <= 2)([1, 2]);
// true
some(x => x <= 2)(new Set([1, 2]));
// true
some(x => x <= 2)(
  new Map([
    ['a', 1],
    ['b', 2],
  ]),
);
// true
some(x => x === '1')('12');
// true

Iterator

Iterator allows you to chain operations more easily. It supports all these methods:

• drop
• take
• map
• filter
• every
• some
• reduce
• find
• len
• forEach

You can also use the method build() to reconstruct an iterable (either from the same type as the input, or you can transform it).

Supported iterables

• array
• string
• Map
• Set
• Object
• iterators

Examples

const iterable = Iterable.from([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
iterable
  .drop(1)
  .filter(x => x % 2 === 0)
  .map(x => x * 3)
  .take(2)
  .build();
// [6, 12]

build() accepts an optional parameter type:

const iterable = Iterable.from([1, 2, 3]);
iterable.build(type.Set);
// Set([1, 2, 3])