Passing Parameter Onclick, In A Loop

Im creating input elements in a loop. On click, these buttons are supposed to call a certain function with a certain Parameter, based on the Initial creation of the button element.

Solution 1:

You need to use an IIFE and create a new closure like

for (var i = 0; i < planets.length; i++){
  var id = planets[i].id;

  var input = document.createElement("input");
  input.type = "button";
  input.className = "worldButton";
  input.value = "Choose this world";
  
  input.onclick = (function(id, planets){
     return function(){
         game.pickWorld(planets, id);
     }
  })(id,planets);
}

What was happening is the variables planets and id were visible to the callback function and at execution time, were using the last iterated value.

However, with a closure, you effectively created a 'private' variable seen and preserved by each callback function.

Solution 2:

You need to pass the id and planets variables in the function like:

for (var i = 0; i < planets.length; i++){
  var id = planets[i].id;

  var input = document.createElement("input");
  input.type = "button";
  input.className = "worldButton";
  input.value = "Choose this world";
  Input.onclick = (function(pl, id){
     game.pickWorld(pl, id);
  })(planets, id);
}

You can read more about IIFE in this article.