javascript parameter is undefined

Question

In line 16, setText, it says that TypeError: Cannot read property 'toString' of undefined and im not sure how to fix that. Also line 30, the last for loop says that i is already defined but im not sure how.

//lists
var teamNames = getColumn("NBA Teams", "Team");
var teamChampionships = getColumn("NBA Teams", "Championship wins");
var teamConference = getColumn("NBA Teams", "Conference");
//filteredList
var filteredNames = [];

onEvent("userButton", "click", function( ) {
  updateScreen();
});
//updates screen to show filtered team names
function updateScreen(){
  var textOutput = "";
  var championship = getColumn("NBA Teams", "Championship wins");
  textOutput = findMatches(championship);
  setText("teamsArea", textOutput);
}
for (var i = 0; i < teamNames.length; i++) {
  if (teamConference == getText("conferenceDropdown") && teamChampionships == getNumber("championshipInput")) {
    appendItem(filteredNames, teamNames[i]);
  }
}

//macthes data input with teams and returns it
//championship (integer) - user inputs numbert of championshops
//matches (string) - name of matching teams based on inputed date
function findMatches(championship) {
  var teamNames = getColumn("NBA Teams", "Team");
  var matches = filteredNames[i];
  for (var i = 0; i < teamNames.length; i++) {
    if (championship == getNumber("championshipInput")) {
      return matches;
    }
  }
}

Answer 1

welcome to StackOverFlow :-)

Ok, so you may want to trace things back to, these two lines:

var championship = getColumn("NBA Teams", "Championship wins");
textOutput = findMatches(championship);

Either 'getColumn' is returning "undefined" or an empty array [] or:

textOutput = findMatches(championship); // returns undefined...

I noticed that the "findMatches" function does not have a defined return value, if false.

  function findMatches(championship) {
      var teamNames = getColumn("NBA Teams", "Team");
      var matches = filteredNames[i];
      for (var i = 0; i < teamNames.length; i++) {
          if (championship == getNumber("championshipInput")) {
              return matches;
          }
      }
      // will return undefined, if for loop never returns "matches"...
   }

Without more clarification as to the markup and the remainder of the referenced functions such as getColumn, setText, etc. That looks like a good place to start.

As for line 30... that is because you already defined a variable "i" on line 18, and then on line 30 attempt to redefine it...

I would suggest using "let" for blocks and loops 'let'...