The array type of the JS reference type

//The 1.concat () method does not change the original array, copying a copy of the original array to splicevararr = [' Red ', ' Zhansan ', ' Xin '];varARR2 = Arr.concat (' 2 ', [' 3 ', ' 9 ']); Console.log (arr); //[' Red ', ' Zhansan ', ' Xin ']Console.log (ARR2);//[' Red ', ' Zhansan ', ' Xin ', ' 2 ', ' 3 ', ' 9 ']//The 2.slice () method does not change the original array, with two parameters, the result of the interception contains the head without the tail, only one parameter, the Intercept is from the parameter specified position to the end of the current array of all itemsvarARR3 = [' sasd ', ' 2 ', ' Zan ', ' Xin '];varARR4 = Arr3.slice (1);varARR5 = Arr3.slice (1, 3); Console.log (ARR4); //[' 2 ', ' Zan ', ' Xin ']Console.log (ARR5);//[' 2 ', ' Zan ']//3.splice () method inserts data into the middle of the arrayvararr6=[1,2,3,4,5]//DeletevarArr7=arr6.splice (0,2)//Delete the first two items of an arrayConsole.log (ARR7)//[1, 2]Console.log (ARR6)//[3, 4, 5] The original array arr6 is changed//Insert//Splice (start position, number of items to be deleted, items to insert, items to insert,...)vararr8=[2,3,4,6]varArr9=arr8.splice (2,0, "red", ' oo ')//the current array position 2 item is deleted, and then the string red and OO are inserted starting at position 2Console.log (ARR9)//Empty ArrayConsole.log (ARR8)//[2, 3, ' red ', ' oo ', 4, 6] Change the original array//Replace//Splice (start position, number of items to be deleted, items to insert, items to insert,...) The inserted item does not have to be equal to the deleted itemvararr10=[1,2, ' A ', ' ASD '];varArr11=arr10.splice (1, 2, "Hello", ' Hai '); Console.log (ARR11)//[2, ']Console.log (ARR10)//[1, ' Hello ', ' hai ', ' asd ']//4. Position Method IndexOf () LastIndexOf () returns 1 when comparing the first parameter to each item of the array, must use the congruent = = =varnumbers=[1,2,3,4,5,6,4,7,8];console.log (Numbers.indexof (4))//location is 3Console.log (Numbers.lastindexof (4))//location is 6//5. Iterative Methodsvarnum=[1,2,3,4,6,4,3,2,1];varResult=num.filter (function(Item,index,arr) {return(Item >2)//values greater than 2 in the array form a new array}) Console.log (Result)//[3, 4, 6, 4, 3]varResult1=num.map (function(Item,index,arr) {return(item*2)//Array Values All * * Create a new array}) Console.log (RESULT1)//[2, 4, 6, 8, A, 8, 6, 4, 2]varResult2=num.foreach (function(Item,index,arr) {Console.log ("Item" +item+ "-index" +index+ "-arr:" +arr)//the array is similar to the For Loop//item1-index0-arr:1,2,3,4,6,4,3,2,1//item2-index1-arr:1,2,3,4,6,4,3,2,1//item3-index2-arr:1,2,3,4,6,4,3,2,1//item4-index3-arr:1,2,3,4,6,4,3,2,1//item6-index4-arr:1,2,3,4,6,4,3,2,1//item4-index5-arr:1,2,3,4,6,4,3,2,1//item3-index6-arr:1,2,3,4,6,4,3,2,1//item2-index7-arr:1,2,3,4,6,4,3,2,1//item1-index8-arr:1,2,3,4,6,4,3,2,1})//6. Merge method The function of reduce () Reduceright () accepts 4 parameters, the previous value, the current value, the index of the item , and the array objectvarval=[1,2,3,4,5,6,7,8,9,10];varSum=val.reduce (function(Prev,cur,index,arr) {returnprev+cur;}) Console.log (sum)// -

The array type of the JS reference type