做 javascript arrays 克隆

Question

I have two arrays as parameters and need to add each element from the add array to the main array, sort the main , then remove that element, and repeat (add the next element of add array to main array).

function twoArrays(main, add) {
  var tempArr =[];
  for(var i=0; i<main.length; i++){ 
    tempArr.push(main[i]);
  }

  for(var i=0; i<add.length; i++){ 
    main.push(add[i]);
    main = main.sort(function(a, b){return b - a}); 
    console.log(main); 
    main = [];
    main = tempArr; 
  } 

}


var main =[ 100, 100, 50, 40, 40, 20, 10 ] 
var add = [99, 44,33,22,9]
twoArrays(main, add);

My problem is this statement main = tempArr; is not working the way I think it should. I expect to delete main ( main = []; ), and then populate main with tempArr ( main = tempArr; ). However, I get the previous main, with add items in it, notice the 99, 44, 33, 22 as follows

 100,100,99,50,40,40,20,10
 100,100,50,44,40,40,20,10
 100,100,50,44,40,40,33,20,10
 100,100,50,44,40,40,33,22,20,10
 100,100,50,44,40,40,33,22,20,10,9

Answer 1

As others have said, you're losing reference to the original main when you do main = [] . If you want to reset the array, and do a new transformation (add an element from add to main , sort, then reset), try this instead:

 function twoArrays(main, add) { for(var i=0; i<add.length; i++){ let clone = [...main]; clone.push(add[i]); clone.sort(function(a, b){return b - a}); console.log(clone); } } const main =[ 100, 100, 50, 40, 40, 20, 10 ] const add = [99, 44,33,22,9] twoArrays(main, add);

Answer 2

When you do main = tempArr; main and tempArr both point to the same array. To copy the tempArr in main, instead of main = []; main = tempArr; main = []; main = tempArr; do main = [..tempArr];