Add / remove / filter / sort array elements

add to / Delete / Screening / Sort array elements

1. Continue adding elements at the end of the array push

   var arr = [1,2,3];
   arr.push(4,5,'kkk');
   console.log(arr);
   

2. Add elements at the beginning of the array unshift
   

   var arr = [1,2,3];
   arr.unshift('red');
   console.log(arr);
   

3. Delete the last element of the array pop()

   arr.pop();  // No need again （） Write any element in 
   

4. Deletes the first element of the array shift()

   arr.shift();  // No need again （） Write any element in 
   

5. Filter array , The elements in the following array Greater than 2000 The deletion of , Put the rest in the new array

   var arr = [1000,2000,2000,3200,4000,1022];
   var newArr = [];  // Define a new array 
   for ( var i = 0; i < arr.length; i++){
         
   	if (arr[i] < 2000) {
         
   		newArr.push(arr[i]);  // If it is less than 2000, Just add it to the new array （i It's from 0  At the beginning , So less than 2000 It is equivalent to including 2000）
   	}
   }
   console.log(newArr);
   

6. Array sorting

   var arr = [100,20,3000];
   // Reverse sort  [3000,20,100]
   arr.reverse();  
   // Bubble sort  [20,100,3000]  Fixed writing   Just a reporter 
   arr.sort(function(a,b){
         
   	return a-b; // In ascending order 
   	//return b-a; // In descending order 
   });