lodash - KeynesYouDigIt/Knowledge GitHub Wiki

Vocab

• Collection - Array, object, or string
• Iteratee - Invoked for every element, returns something
• Predicate - Returns true or false
• Comparator - Returns -1, 0, or 1
• Where-style callback - Passing an object to match, using &&
• Pluck-style callback - Passing a string to match

Functions

Searching

• find - Find a matching element: String value, where object, or function
  • findLast - Get the last element returning true for predicate
  • findIndex - Get the index of the first matching element
  • findLastIndex - Get the index of the last matching element
  • indexOf - Get the index of a matching value
  • lastIndexOf - Get the last index of a matching value
• last - Get the last element
• nth - Get the element at an index
• findKey - Get key of matching object
  • findLastKey - Get key of last matching object
• endsWith - Checks if a string ends with a string
• min / max - Find the object with the most/least, value or function

Chopping Up Collection

• take - Get n elments from the beginning
  • takeWhile - Get elements from the beginning until condition is met
  • takeRight - Get elements from the end until condition is met
  • takeRightWhile - Get elements from the end until condition is met
• chunk - Splits an array into sized chunks
• first / head - Get the first element
  • initial - get all but the last element
• tail - All but the first elment

Transform Collection

• map - Transform each element in an array
  • flatMap - Maps a collection and flattens the result
  • flatMapDeep - Flattens deep
  • flatMapDepth - Flattens to specified depth
  • invokeMap - Calls a method for each item in a collection
• reduce - Accumulate a collection
  • reduceRight - Accumulate a collection starting at the end
• groupBy - Creates an object where the keys are groups returned by an iteratee, takes a pluck-style callback, or a function returning a key to group on
  • Good for running reports
• keyBy - Create an object where the keys are determined by an iteratee
• partition - Split a collection into items that return truthy/falsy for a predicate

Transform Array

• flatten - Flatten arrays 1 level deep
  • flattenDeep - Flatten arrays recursively
  • flattenDepth - Flatten arrays n levels deep
• zip - Group an array of values by object
  • unzip - Create an array of values by property
  • unzipWith - Create an array of values by property, specify how properties are combined
  • zipWith - Create an array of values by object, specify how properties are combined
  • zipObject - Create an object with keys
  • zipObjectDeep - Create an object with keys, supports using paths
• concat - Combine arrays
• fill - Fill all elements of the array with a value
• fromPairs - Make an object from key-value array pairs
• reverse - Reverse order (mutates)
• join - Turn into a separated string

Transform Object

• toPairs / entries - Make an array of key-value pairs from object
  • toPairsIn / entriesIn - Include inherited properties
• mapKeys - Change all the keys of an object
  • mapValues - Change all the values of an object
• pick - Get only matched properties from an object
  • pickBy - Get properties where the predicate returns true
• omit - Get everything but matched properties from an object
  • omitBy - Get everything but properties that match a predicate
• transform - Reduce, but for objects, iterates over properties
• invert - Swap keys and values
  • invertBy - Swap keys and values with a supplied transformation
• castArray - Converts to a collection

Transform Number

• clamp - Constrain number with upper and lower bounds
• min, max, minBy, maxBy, ceil, floor, sum, sumBy, mean, meanBy, round
• add, subtract, divide, multiply

Transform String

• escape, escapeRegExp
• startCase, camelCase, capitalize, kebabCase, lowerCase, lowerFirst, upperFirst, snakeCase, toLower, toUpper, upperCase
• replace, template
• repeat
• pad, padEnd, padStart, trim, trimStart, trimEnd
• parseInt, split
• deburr - Remove diacritical marks

Transform Between

• toArray, toFinite, toInteger, toLength, toNumber, toPlainObject, toSafeInteger, toString

Filtering

• filter - Get an array of all elements returning truthy for predicate - function, property to check, where-style callback
  • reject - Remove all elements returning truthy for predicate
  • where - Return all matches for an object
• compact - Removes all falsey values
  • Useful for plucking out properties
• pull - Remove all elements matching value (mutates)
  • pullAll - Remove all elements matching values, like difference
  • pullAllBy - Remove all elements matching values, accepts function or string for key to compare
  • pullAllWith - Remove all elements matchings values, accepts a comparator
  • pullAt - Remove and return all elements at indexes
  • remove - Remove all elements matching predicate, like filter
• without - Remove all matching values
• remove - Remove values matching predicate
• slice - Get a subset of an array
• uniq - Get unique values, takes a property string or function
  • uniqBy
  • uniqWith
  • sortedUniq - Optimized for sorted arrays
  • sortedUniqBy - Optimized for sorted arrays
• drop - Drops elements from beginning
  • dropWhile - Drop until condition is met
  • dropRight - Drops elements from end
  • dropRightWhile - Drops elements from end until condition is met

Predicates

• every - Returns true if all elements in the collection return true for predicate
• includes - Returns true if a collection contains a match
• some - Returns true if at least one of the elements is truthy for the predicate
  • Useful for pre-flight checking an expensive calculation
• eq, gt, lt, gte, lte
• isEmpty
• conformsTo - Checks if properties conform to rules
• isArray, isArrayLike, isArrayBuffer, isArrayLikeObject
• isBoolean, isNan, isFinite, isInteger, isFunction, isLength, isMap, isNative, isNil, isNull, isNumber, isObject, isObjectLike, isPlainObject, isRegExp, isSafeInteger, isSet, isString, isTypedArray, isUndefined, isWeakMap, isWeakSet
• isMatch - Partial comparison
  • isMatchWith - Partial comparison, custom comparer
• eq - Compares values
  • isEqual - Deep comparison
  • isEqualWith - Custom comparison
• inRange - Checks if a number is in range

Set Operations

• difference - Get values from one array that aren't in others- get all matches
  • differenceBy - Accepts a property or function returning the string to compare with
  • differenceWith - Accepts a comparator
• intersection - Get values that are in all arrays
  • intersectionBy - Accepts a property or function returning the string to compare with
  • intersectionWith - Accepts a comparator
• union - Get unique values from all arrays
  • unionBy - Accepts a property or function returning the string to compare with
  • unionWith - Accepts a comparator
• xor - Returns elements that aren't in all arrays
  • xorBy - Accepts a property or function returning the string to compare with
  • xorWith - Accepts a comparator

Organize

• shuffle - Randomize the order of a collection
• sortBy - Sorts a collection by a property, accepts string or function, accepts an array for multiples
  • sortedIndex - Lowest index you can insert at and maintain sort order, use with splice
    • sortedIndexBy - Accepts a function or string for property to look at
    • sortedIndexOf - sortedIndex, but the array should already be sorted
    • sortedLastIndex - Highest index
    • sortedLastIndexBy
    • sortedLastIndexOf
  • Is immutable, unlike .sort()
• orderBy - Sort, specificying sort direction

Iteration

• each / forEach - Standard loop, early exit by returning false
  • forIn - Only own properties
  • forOwn - Only own properties
  • eachRight / forEachRight - Standard loop, backward
• forOwn - Objects, no inherited properties
  • forOwnRight - Objects, no inherited properties in reverse
• forIn - Objects, also inherited properties
  • forInRight - Objects, also inherited properties in reverse
• range - Make an array with a range of numbers
  • rangeRight - Reverse

Analyze

• countBy - Iterate through a collection and count the number of times a given property is returned
• size - Get the size of a collection
• sample - Get a random element
  • sampleSize - Get random elements
• random - Generate a random number

Build Object

• create - Create an object with a particular prototype
• assign - Combine objects, clobbering from left to right. Mutates.
  • assignIn / extend - Also inherited properties
  • assignWith / extendWith - Customizes the assignment
  • assignInWith - Also inherited properties, customizes the assignment
• defaults - Doesn't clobber
  • defaultsDeep - Recursive
• merge - Also inherited properties, recursive, doesn't clobber if undefined
  • mergeWith - Also inherited properties, recursive, doesn't clobber if undefined, customizes the assignment
• clone - Shallow clone
  • cloneWith - Shallow clone with customizer
  • cloneDeep - Deep clone
  • cloneDeepWith - Deep clone with customizer

Object Properties & Methods

• at - Get all properties at particular paths (eg. "someProperty.someOtherProperty[dynamicProperty]")
• get - Get a property at a particular path (eg. "someProperty.someOtherProperty[dynamicProperty]"), with default
• result - Get property at a particular path, invoking it if it's a function
• has - Check if an object has a path
  • hasIn - Check if an object or its prototypes have a path
• set - Set the value at a path
  • setWith - Set the value at a path, accepting a customizer for the path
• update - Set, but accepts a function to change the value
  • updateWith - Set, but accepts a function to change the value, accepting a customizer for the path
• unset - Remove a property, mutates
• invoke - Invoke the method at a path of an object
• keys - Get the keys of an object
  • keysIn - Get the keys of an object and its prototypes
• values - Get the values of an object
  • valuesIn - Get the values of an object and its prototypes
• functions - List functions declared on the object
  • functionsIn - List all functions, owned and inherited