Lodash Methods

# Lodash Story.md

Lodash Story

Exercises: https://karisantos.github.io/book/learning/week3/lodash-drills.html
— by Abhisek Pattnaik <[email protected]>

Datatype Check.md

• isNumber - check for number or NaN value
• isMap - check for Map type
• isFunction - check for function value
• isNull - check for null value
• isNil - check for null or undefined value
• isNaN - check for NaN value
• isError - check for Error type
• isSet - check for Set type
• isDate - check for Date type

Extract Part of Array.md

• take - takes the n number of elements from left
• takeRight - takes the n number of elements from right
• takeWhile - starts takes elements from left till predicate function is truthy
• takeRightWhile - starts takes elements from right till predicate function is truthy
• slice
• first or head - gets the first element
• last - gets the last element
• initial - gets all but last element
• tail - gets all but first element

Function Usage.md

fp.flatMap

pickDeepAll.md

Example

const obj = {
  id: '123',
  from: {
    user: 'abhisekp'
  },
  'from.user': 'Tommy'
}

console.log(
  pickDeepAll(['id', 'from.user', {
    from_user: 'from.user'
  }], obj)
);
/*
{
  from.user: "Tommy",
  from_user: "Tommy",
  id: "123"
}
*/

console.log(
  pickDeepAll('id', obj)
);
/*
{
  id: "123"
}
*/

---

Algorithm

const pickDeepAll = _.curry((props, obj) => {
	const propList = _.concat([], props);
	const [propStrings, propObjs] = _.partition(_.isString, propList);

	const picked1 = _.pickAll(propStrings, obj);
	const picked2 = _.reduce((pickedObj, propMap) => {
		const mappedObj = _.mapValues(_.get(_, obj), propMap);

		return Object.assign(pickedObj, mappedObj);
	}, {}, propObjs);

	return Object.assign(picked1, picked2);
});

Summing the separated nums.js

const arr = [
  "0002-0002-0003-0004",
  "5874-1734-1294-0004",
  "4234-9999-1234-1234",
  "4346-1234-1004-5884",
  "0002-0002-0004-0003"
]

/*
1. split the array elements at `-` to 2D array
   [["0002","0002","0003","0004", ..., ...]
2. Parse each inner array elements to numbers
   [[2, 2, 3, 4], ..., ...]
3. Sum each array
   [11, 8906, 16701, 12468, 11]
*/

const _ = require('lodash/fp');

const sums = _.map(_.flow(
  _.split('-'),
  _.map(_.toNumber),
  _.sum
));

console.log(sums(arr));
//=> [ 11, 8906, 16701, 12468, 11 ]

z# common-methods.md

Frequently used Lodash methods

I use the following methods frequently in the Lodash fp library

1. curryN
2. partial
3. defaults
4. first
5. get
6. concat
7. filter
8. every
9. includes
10. tap
11. set
12. flow
13. map
14. pick
15. constant
16. identity
17. noop