JS: Array.prototype

What is Array.prototype

Array.prototype is the value of the property key "prototype" of the function Array. 〔see Array Object〕

Array.hasOwnProperty ( "prototype" ) 

Type

Type of Array.prototype is Object .

typeof Array.prototype === "object"

Array.prototype is a true array. Meaning, you can push elements to it, and with a magical length property.

console.log(Array.isArray(Array.prototype));

console.log(Array.prototype.length === 0);

Array.prototype.push("x");

console.log(Array.prototype[0] === "x");

console.log(Array.prototype.length === 1);

Parent

Parent of Array.prototype is Object.prototype .

// parent of Array.prototype
console.log(
 Reflect.getPrototypeOf ( Array.prototype ) === Object.prototype
);

Purpose

Array.prototype is the parent of all array objects.

console.log(
Reflect.getPrototypeOf ( [3,4,5] ) === Array.prototype
);

Purpose of Array.prototype is to provide methods and properties useful for all array objects

〔see Understand JS Array〕

Properties

Value Properties

• length
• constructor
• [Symbol.iterator]
• [Symbol.unscopables]

Function Properties

modify elements

• pop
• push
• shift
• unshift
• splice
• fill
• copyWithin

concat and subarray

• concat
• slice

get elements

• entries
• keys
• values
• [Symbol.iterator] (same as values)

map

• map
• forEach
• filter

sort, reverse

• sort
• reverse

find element

• includes (find by value, return boolean)
• indexOf (find by value, return index)
• lastIndexOf
• find (find by function, return value)
• findIndex (find by function, return index)

true false on all

• some
• every

reduce to single value

• reduce
• reduceRight

convert to string

• join
• toString
• toLocaleString

• [ Symbol.unscopables ]

flatten

• flat
• flatMap