Collections

Finding

_.filter(list, (n) => n % 2)    // → Array
_.find(list, (n) => n % 2)      // → item
_.findRight(list, ...)          // → item

Works for both arrays and objects.

Accessing

_.at([ abcd ], 0)               // → [ a ] - same as list[0]
_.at([ abcd ], [ 0, 1 ])        // → [ ab ]

Set/get

_.set(object, 'users[0].name', value)
_.get(object, 'users[0].name')
_.get(object, ['users', 0, 'name'])

Iteration

_.forEach(list, (item, i) => ...)
_.forEachRight(list, ...)

_.map(list, ...)
_.every(users, (u) => u.active)  // → true|false (aka _.all)
_.any(users, ...)                // → true|false (aka _.some)

Array

Arrays

_.chunk([ abcd ], 2)           // → [ [ab], [cd] ]
_.compact(list)

_.fill(Array(4), 'x')          // → [ 'x', 'x', 'x', 'x' ]
_.flatten
_.flattenDeep

Filtering

_.drop([ abcdef ], 2)          // → [   cdef ]
_.dropRight([ abcdef ], 2)     // → [ abcd   ]
_.take([ abcdef ], 2)          // → [ ab     ]
_.takeRight([ abcdef ], 2)     // → [     de ]
_.slice([ abcdef ], 2, 4)      // → [   cd   ]
_.initial([ abcdef ])          // → [ abcde  ] - dropRight(list, 1)
_.rest([ abcdef ])             // → [  bcdef ] - takeRight(list, 1)
_.dropWhile(list, 'active')            // works like filter
_.dropWhile(list, 'active', true)
_.dropWhile(list, { active: true })
_.dropWhile(list, (n) => ...)
_.dropRightWhile(list, ...)
_.without([ abcde ], b)        // → [ acde ]
_.remove(list, (n) => n % 2)

Accessing

_.first([ abcdef ])            // → a
_.last([ abcdef ])             // → f

Sets

_.uniq()
_.difference([ abc ], [ bc ])       // → [ a    ]
_.intersection([ abc ], [ bcd ])    // → [  bc  ]
_.union([ abc ], [ bcd ])           // → [ abcd ] (unique)
Array#concat()

Indexes

_.findIndex(list, fn)
_.findLastIndex(list, fn)
_.sortedIndex(list, val)
_.sortedLastIndex(list, val)
_.indexOf(list, val)

Functions

Currying

greet = (greeting, name) => `${greeting}, ${name}!`
fn = _.partial(fn, 'hi')
fn('joe')    // → 'hi, joe!'

fn = _.partial(fn, 'joe')
fn('yo')     // → 'yo, joe!'
_.curry(greet)('hi')         // → function(name)
_.curryRight(greet)('joe')   // → function(greet)

Decorating functions

Throttling

_.throttle(fn)
_.debounce(fn)

Limiting

_.before(5, fn)         // only works 5 times
_.after(5, fn)          // works only after 5 times
_.once(fn)              // like _.before(fn, 1)

Etc

_.wrap(_.escape, (name) => `hi ${name}`)
// same as doing `name = _.escape(name)`

_.delay(fn, 2000)

_.negate(fn)

_.memoize(fn)
_.memoize(fn, ...)

Strings

Capitalization

_.capitalize('hello world')   // → 'Hello world'
_.startCase('hello_world')    // → 'Hello World'
_.snakeCase('hello world')    // → 'hello_world'
_.kebabCase('hello world')    // → 'hello-world'
_.camelCase('hello world')    // → 'helloWorld'

Padding

_.pad('abc', 8)           // → '   abc  '
_.padLeft('abc', 8)       // → '     abc'
_.padLeft('abc', 8, '-')  // → '00000abc'
_.padRight(...)

Trim

_.trim('  str  ')
_.trimLeft('  str  ')
_.trimRight('  str  ')

Etc

_.repeat('-', 2)              // → '--'
_.deburr('déjà vu')           // → 'deja vu'
_.trunc('hello world', 5)     // → 'hello...'
_.startsWith('abc', 'a')   // → true
_.endsWith('abc', 'c')     // → true

Objects

Keys and values

_.keys(obj)
_.values(obj)

Chaining

Chain and value

_([1, 2, 3])
  .reduce((total, n) => total + n)
  .map((n) => n * n)
  .tap(console.log)
  .thru((n) => n.reverse())
  .value()
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