Lotide

A mini clone of the Lodash library.

Purpose

BEWARE: This library was published for learning purposes. It is not intended for use in production-grade software.

Usage

Install it:

npm install @jinwonn/lotide

Require it:

const _ = require('@jinwonn/lotide');

Call it:

const results = _.tail([1, 2, 3]) // => [2, 3]

Documentation

The following functions are currently implemented:

• countLetters(string): return an object of counts of each of the letters from string (excluding spaces).

    _.countLetters('sttr');
    // => {s:1,t:2,r:1}
  
    _.countLetters('s t tr');
    // => {s:1,t:2,r:1});

• countOnly([allItems], {itemsToCount}): Returns and array of counts for items specified in {itemsToCount} from inputted collection of items (strings) in [allItems].

    const firstNames = ["Karl", "Salima", "Agouhanna", "Fang","Kavith", "Jason", "Salima", "Fang", "Joe"];
  
    const result1 = _.countOnly(firstNames, { "Jason": true, 
                                              "Karima": true, 
                                              "Fang": true, 
                                              "Agouhanna": false 
                                            });
  
    result1["Jason"]; // => 1
  
    result1["Karima"]; // => undefined
  
    result1["Fang"]; // => 2
  
    result1["Agouhanna"]; // => undefined

• eqArrays([actual], [expected]): Takes in two arrays and returns true or false, based on a perfect match.

    _.eqArrays([1, [[2], 3]], [1, [[2], 3]]);// => true
  
    _.eqArrays([1, 2, [3]], [[3], 2, 1]);// => false
  
    _.eqArrays(["1", "2", [3]], ["1", 2, [3]]); // => false

• eqObjects({actual}, {expected}) Takes in two objects and returns true or false, based on a perfect match.

    const ab = { a: "1", b: [2, 3], c: {4 ,5} };
    const ba = { b: [2, 3], c: {4 ,5}, a: "1" };
      
    _.eqObjects(ab, ba); // => true
  
    const abc = { a: "1", b: [2, 3], c: {4 ,5}, d: "6" };
      
    _.eqObjects(ab, abc); // => false

• findKey({input}, cb): Returns the first key from {input} for which the cb returns a truthy value.

    const input = { "Blue Hill": { stars: 1 },
                    "Akaleri":   { stars: 3 },
                    "noma":      { stars: 2 },
                    "elBulli":   { stars: 3 },
                    "Ora":       { stars: 2 },
                    "Akelarre":  { stars: 3 }
                  };
  
    _.findKey(input, x => x.stars === 2); // => "noma"
      
    _.findKey(input, x => x.stars === 4); // => undefined

• findKeyByValue({data}, searchKey): Returns the first key from {data} which contains the given value searchKey.

    const bestTVShowsByGenre = { sci_fi: "The Expanse",
                                 comedy: "Brooklyn Nine-Nine",
                                 drama:  "The Wire" };
  
    _.findKeyByValue(bestTVShowsByGenre, "The Wire");
    // => drama
  
    _.findKeyByValue(bestTVShowsByGenre, "That '70s Show");
    // => undefined

• flatten([input]): Returns a flattened single-level array from [input] which contains other arrays inside.

    _.flatten([1,[2,3],'a',[5],true]);
    // => [1,2,3,'a',5,true])

• head([input]): Returns the first element of [input].

    _.head([1, a, 3]); // => 1
  
    _.head([]); // => undefined

• letterPositions(string): returns an object of arrays of all the indices (zero-based positions) in string where each character is found (excluding spaces).

    _.letterPositions('lighthouse labs');
    // => {l: [ 0, 11 ],
           i: [ 1 ],
           g: [ 2 ],
           h: [ 3, 5 ],
           t: [ 4 ],
           o: [ 6 ],
           u: [ 7 ],
           s: [ 8, 14 ],
           e: [ 9 ],
           a: [ 12 ],
           b: [ 13 ]}

• map([input], cb): Returns a new array based on the results of callback function cb on [input].

    const words = ["ground", "control", "to", "major", "tom"];
  
    _.map(words, word => word.length);
    // => [6,7,2,5,3]

• middle([input]): Return an array with only the middle element(s) of [input].

    _.middle([1]);
    // => []
  
    _.middle([1, 2]);
    // => []
  
    _.middle([1, 2, 3]);
    // => [2]
  
    _.middle([1, 2, 3, 4]);
    // => [2, 3]

• tail([input]): Gets and returns an array of all but the first element of [input].

    _.tail([1, a, 3]); // => [a, 3]

• takeUntil([input], cb): return a "slice of [array] with elements taken from the beginning until the cb returns a truthy value.

    const data1 = [1, 2, 5, -1, 2, 4, 5];
      
    _.takeUntil(data1, x => x < 0);
    // => [ 1, 2, 5 ]
  
    const data2 = ["I've", "been", "to", "Hollywood", ";", "also", "Redwood"];
      
    _.takeUntil(data2, x => x === ';');
    // => [ "I've", 'been', 'to', 'Hollywood' ]

• without([source], [itemsToRemove]): Returns an array of values from [source] excluding all given values in [itemsToRemove].

    _.without([1, 2, 3], [1]);
    // => [2, 3]
  
    _.without(["1", "2", "3"], [1, 2, "3"]);
    // => ["1", "2"]