JavaScript: Array.prototype

Array.prototype is the value of the property key "prototype" of the function Array.

[see Array Object]

console.log( Array.hasOwnProperty ( "prototype" ) ); // true

Type

Type of Array.prototype is Object .

console.log( typeof Array.prototype === "object" ); // true

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 ) ); // true

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

Array.prototype.push ( "a", "b" );

console.log( Array.prototype ); // [ 'a', 'b' ]

console.log( Array.prototype.length === 2 ); // true

Parent

Parent of Array.prototype is Object.prototype .

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

Purpose

Array.prototype is the parent of all array objects.

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

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

[see Understand JS Array]

Properties

Value Properties

• length
• constructor

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