JS learning notes -- bottom implementation of array method

push – Tail add

Returns the length value of an array

			Array.prototype.myPush = function(val) {
    
				if (arguments.length && arguments.length > 1) {
    
					for (let i = 0; i < arguments.length; i++) {
    
						this[this.length] = arguments[i]
					}
				} else {
    
					this[this.length] = val
				}
				return this.length
			}

pop Tail delete

Only one... Can be deleted , And return the deleted element

			//  Tail delete 
			Array.prototype.myPop = function() {
    
				//  Delete the last element   And return the currently deleted element 
				console.log('11==',this)
				const val=this[this.length-1]
				this.length--
				return val
			}

unshift Add... To the head

Return array length

			Array.prototype.myUnshift = function(val) {
    
				const len = arguments.length
				const len1 = this.length
				if (len1) {
    
					//  The array length is greater than 0, All elements move back 
					if (len) {
    
						for (let i = len1 - 1; i >= 0; i--) {
    
							// const temp=this[i]
							this[i + len] = this[i]
						}
						for (let i = 0; i < len; i++) {
    
							this[i] = arguments[i]
						}
					}
				} else {
    
					//  The length of the array is equal to 0
					if (len) {
    
						for (let i = 0; i < len; i++) {
    
							this[i] = arguments[i]
						}
					}
				}
				return this.length
			}

shift Head delete

No parameter , Return the currently deleted element value

			Array.prototype.myShift=function(){
    
				for (var i = 0; i < this.length-1; i++) {
    
					this[i]=this[i+1]
				}
				const val=this[0]
				this.length--
				return val
			}

splice Delete Replacement elements Insert elements

Return deleted elements The first parameter Starting element coordinates , The second element Delete the number of elements , Third to third N individual , Replaced or added elements

Ongoing update