Quick Overview

Javascript arrays are iterable collections containing variable data types and resizable as per requirement. They inherit from Array.prototype which is it's object type. It provides a number of useful members for various operations on these objects.

Creation

• new   Array(...arg)    length (single arg) or values (multiple args)
• Array.from(...itr)      shallow copy of any iterable
• Array.of(...values)      expands and combines all values

General Property/Methods

• arr.length
• arr.at
• arr.sort( comp_fun(first,second) )    Takes reference to a function, sorts in occurence order if returned value > 0 , otherwise reverse order
• arr.reverse()    In place reversal of original order

Mutation

• arr.push()     append end
• arr.pop()      remove last
• arr.unshift(...args)   add multiple beginning
• arr.shift()      remove first
• arr.splice( start,del_count,...items )    starting at given index delete any no. or add any no. of new elements
• arr.concat(...items)    appends multiple values or arrays (merge)
• arr.fill( val )      all elements changed to val

Search/Existence

• arr.indexOf()      index or -1 if not exists
• arr.find( test_fun )      first match (element) passing callback or undefined
• arr.findIndex( test_fun )    index of first callback pass or -1
• arr.findLast( test_fun )      last test function pass(element) or undefined
• arr.findLastIndex( test_fun )    index of last callback pass or -1

Conversion

• arr.join( sep )      Array to String with elements concatenated using seperator | default : ','
• arr.toLocaleString()      array to string including commas
• str.split( sep )    string to array using separator to split into elements

Iteration

• arr.forEach( callback )    iterates over array items & executes callback with args - element,index & array
• arr.values()    returns an iterator to object values [non-mutating]
• str.keys()    returns iterator to object keys/indices
• arr.entries()    returns iterator containing both keys & values as first & second items respectively

Subseting / Testing

• arr.slice( start,end )    sub-array from start upto end (non including) [non-mutating] [shallow-copy]
• arr.filter( callback )    sub-array comprising elements passing callback check [n-m] [s-c]
• arr.includes( val )    boolean representing existence of item
• arr.every( test_fun )    boolean representing test function check value by all items (always true for empty arr)
• arr.some( test_fun )    boolean representing test function pass by atleast 1 item (always false for empty arr)

Transformation

• arr.map( callback )    iterate over each item and returns new array with elements corresponding to values returned by callback in order [n-m]
• arr.reduce( ( prevVal,el,ind,arr)=> ... , initVal )    reducer callback aggregating results of execution previous item, starts iterating from index 1 with 0th element as initVal if not provided explicitly