The difference between arrays and pseudo-arrays in Js

Table of contents

        1. Create objects and arrays

        2. The relationship between objects and arrays

        3. Arrays and pseudo-arrays

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        1. Create objects and arrays

                        create object

let obj1 = {}
let obj2 = new Object()

                        create array

let arr1 = []
let arr2 = new Array()

        2. The relationship between objects and arrays

                        There is a saying that everything is an object. JavaScript has prototype inheritance, and all JavaScript built-in constructors inherit from Object.prototype. Under this premise, it can be understood that new objects (new Array and [ ]) created using built-in object methods all have the property of Object.prototype.

                        

        3. Arrays and pseudo-arrays

                        An array is essentially an ordered collection. The elements of the array can be of any type, but generally when we set up a new array, we keep the elements in the array with the same type.

                        Arrays have a length, and the length is variable. The length of the array length property is a built-in property, all arrays have a length property.

                        Pseudo-array is an object object, which has a length attribute, generally subscripted as an attribute. For example, arguments, and the list of node objects obtained in dom is also a pseudo-array.

                        How to convert a pseudo-array into a real array  

function fn1(a,b,c){
    return Array.prototype.slice.call(arguments)
}

let arr = fn1(1,2,3)
console.log(arr)        //[1,2,3]

function fn2(...arguments){
    return arguments
}
let newArr = fn(1,2,3)

console.log(newArr)   //[1,2,3]

                        Arrays can use all methods of arrays, but pseudo-arrays cannot directly use methods of arrays. You need to convert pseudo-arrays into real arrays before you can use all methods of arrays.