通过比较 Javascript 中的 2 个数组来查找缺失的元素

2022-01-25 00:00:00 arrays compare javascript

由于某种原因，我很难解决这个问题.我需要这个 JS 函数，它接受 2 个数组，比较 2，然后返回缺少元素的字符串.例如.查找 currentArray 中缺少的元素，该元素在前一个数组中存在.

For some reason I'm having some serious difficulty wrapping my mind around this problem. I need this JS function that accepts 2 arrays, compares the 2, and then returns a string of the missing element. E.g. Find the element that is missing in the currentArray that was there in the previous array.

function findDeselectedItem(CurrentArray, PreviousArray){

var CurrentArrSize = CurrentArray.length;
var PrevousArrSize = PreviousArray.length;

// Then my brain gives up on me...
// I assume you have to use for-loops, but how do you compare them??

return missingElement;

}

提前致谢！我不是要代码，但即使只是朝着正确的方向推动或提示可能会有所帮助......

Thank in advance! I'm not asking for code, but even just a push in the right direction or a hint might help...

推荐答案

这应该可行.您还应该考虑数组元素实际上也是数组的情况.indexOf 可能无法按预期工作.

This should work. You should also consider the case where the elements of the arrays are actually arrays too. The indexOf might not work as expected then. 

function findDeselectedItem(CurrentArray, PreviousArray) {

   var CurrentArrSize = CurrentArray.length;
   var PreviousArrSize = PreviousArray.length;

   // loop through previous array
   for(var j = 0; j < PreviousArrSize; j++) {

      // look for same thing in new array
      if (CurrentArray.indexOf(PreviousArray[j]) == -1)
         return PreviousArray[j];

   }

   return null;

}

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