基于javascript中位置的数组差异

Question

I have tried multiple approach to solve this problem, any heads up would be great help. I'm having a drag and drop functionality using ng-draggable.js in my project,so initially I set the elements to array A , and when I drag and drop an element inside the array, I don't know how to capture the changed elements in that array with positions. say A = [1,2,3] now customer changes the position with drag and drop feature. Its becomes B = [2,1,3] . when I do a diff of A and B , I must get the changed elements [2,1] with positions, so that I can send it to server th elements with updated positions. I have tried underscore.js _.difference(A,B) , it gives me empty array,

Answer 1

It seems that .difference() returns set differences, but the index is important here:

 var a = [1,2,3]; var b = [2,1,3]; var diff = a.filter(function(value, index) { return b[index] != value; }); //[1,2] var positions = diff.map(function(value) { return b.indexOf(value); }); // [0,1] 

Then, for each of those values you need to find the position in array b using .indexOf()