Showing identical elements of two arrays in a separate array

Question

I am quite new to JavaScript. What I am trying to achieve here is to put all the identical elements of two array into another array.I then delete those elements in the original two arrays.

However, the separate array does not show all the identical ones.Also, the two arrays still show some identical elements. Not sure where I went wrong.

The following code may have syntax errors. I had to modify it to make it easier to ask.

var finalSelective = ["CS348", "CS353", "CS381", "CS422", "CS448", "CS490-ES0", "CS490-DSO"];
var finalSEelective = ["CS348", "CS352", "CS353", "CS354", "CS381", "CS422", "CS448", "CS456", "CS473", "CS490-DSO", "CS490-ES0"];
var SEelecSelec = []; //fulfills SE elective and S elective.
for (var i = 0; i < finalSelective.length; i++) { //There is something wrong with this one.
  for (var j = 0; j < finalSEelective.length;j++){ //It does not show the correct repeats.
    if (finalSelective[i] == finalSEelective[j]) {
      SEelecSelec.push(finalSEelective[j]);
      var x = finalSelective.indexOf(finalSelective[i]);
      if (x != -1) {
        finalSelective.splice(x,1);
      }
      x = finalSEelective.indexOf(finalSEelective[j]);
      if (x != -1) {
        finalSEelective.splice(x,1);
      }
    }
  }
}

I think you want `===` in javascript and not `==` [Reference](http://stackoverflow.com/questions/359494/does-it-matter-which-equals-operator-vs-i-use-in-javascript-comparisons) — leigero, Apr 21 '16 at 20:22
@leigero It's generally a better idea to use `===` but it doesn't matter in this case. — Mike Cluck, Apr 21 '16 at 20:23

omarjmh · Accepted Answer · 2016-04-21T22:00:21.093

6

Here is another potential solution:

JsBin With Logging

var a = ["CS348", "CS353", "CS381", "CS422", "CS448", "CS490-ES0", "CS490-DSO"];
var b = ["CS348", "CS352", "CS353", "CS354", "CS381", "CS422", "CS448", "CS456", "CS473", "CS490-DSO", "CS490-ES0"];

var c = a.concat(b).filter(function(el) {
  return a.indexOf(el) > -1 && b.indexOf(el) > -1;
});

Edit: Per your comment below, the code to get your actual desired output is:

for (var i = 0; i < a.length; i++) {
  var indexInB = b.indexOf(a[i]);
  if (indexInB > -1){
    output.push(a[i]);
    a.splice(i, 1);
    b.splice(indexInB, 1);
    i--;
  }
}

JsBin with the code above only

edited Apr 21 '16 at 22:00

answered Apr 21 '16 at 20:24

omarjmh

13,632
6
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42

I might be misunderstanding your code, But the output I require is: c = [CS348,CS353,CS381,CS422,CS448,CS490-ES0,CS490-DSO] a = [] and b = [CS352,CS354,CS456,CS473] – Avinash Prabhakar Apr 21 '16 at 21:48
Ignore the first comment. It became too late to edit it. – Avinash Prabhakar Apr 21 '16 at 21:49
1

I am trying to extract the identical elements in array a and b. Then put them in c. the extracted elements must be deleted from a and b. – Avinash Prabhakar Apr 21 '16 at 21:50
ok I added that code, next time if you include your desired output in the question that would be helpful! thanks – omarjmh Apr 21 '16 at 22:00
This is exactly what I am looking for. It is a good solution. Thank you very much. Yes, I will do that next time I ask questions to be more specific. – Avinash Prabhakar Apr 21 '16 at 22:05

score 1 · Answer 2 · answered Apr 21 '16 at 20:35

Here another possible solution. Common values are pushed in a separate array and also get removed from their initial arrays.

var finalSelective = ["CS348", "CS353", "CS381", "CS422", "CS448", "CS490-ES0", "CS490-DSO"],
finalSEelective = ["CS348", "CS352", "CS353", "CS354", "CS381", "CS422", "CS448", "CS456", "CS473", "CS490-DSO", "CS490-ES0"],
SEelecSelec = [],
el, index;

for (var i = 0, len = finalSelective.length; i < len; i++) {
    el = finalSelective[i];

    index = finalSEelective.indexOf(el);

    if (index > -1) {
        SEelecSelec.push(el);
        finalSEelective.splice(index, 1);
        finalSelective.splice(i, 1);
    }
}

console.log(finalSelective, finalSEelective, SEelecSelec);

Plunker here

finalSelective = ["CS353", "CS422", "CS490-ES0"] finalSEelective = ["CS352", "CS353", "CS354", "CS422", "CS456", "CS473", "CS490-ES0"] SEelecSelec = ["CS348", "CS381", "CS448", "CS490-DSO"]. This is what the output shows. But this is not what I need. I need to delete the identical elements in finalSelective and finalSEelective. So ideally, finalSelective should be empty. finalSElective should have CS352,CS354,CS456,CS473 — Avinash Prabhakar, Apr 21 '16 at 22:01

Showing identical elements of two arrays in a separate array

2 Answers2