JavaScript Diff Function Implementation

Since I have not ever done it before, I have found it was not obvious to me how to create a lists diff function in JavaScript, so I feel like should public the solution.

function diff(first, second) {
  var diff = [], start_k = 0;
    
  // calculating the diff
  for (var i=0; i < first.length; i++) {
    var same_found = false;
    var pluses = [];
    for (var k=start_k; k < second.length; k++) {
      if (first[i] == second[k]) {
        same_found = second[k];
        start_k = k+1;
        break;
      } else {
        pluses.push(second[k]);
      }
    }
    if (same_found) {
      for (var j=0; j < pluses.length; j++) {
        diff.push({plus: pluses[j]});
      }
      diff.push({same: same_found});
    } else {
      diff.push({minus: first[i]});
    }
  }
  
  // pushing down the trailing elements
  for (var k=start_k; k < second.length; k++) {
    diff.push({plus: second[k]});
  }

  return diff;
};

this function will return a sequention of hashes with keys 'minus', 'plus', 'same' which represents the differences and similarities between the two incomming arrays