Passing Parameters To Keydown

How can you pass parameters into the keydown method from jquery because whenever I use a variable defined elsewhere it returns undefined. I assume its because the #target is window

Solution 1:

You console.log is not working because it is initialized when the script load. What you need to do is to trigger your functions when the key is pressed.

// When the document is ready
$(function() {
   $(document).keydown(function(e){
      var key = e.which;
      var a = 'a scoped variable';
      switch (key) {
          // Up arrowcase38: 
             a = upArrowFunction(a); // Assign a to the returned value.break;
          // Down arrowcase40:
             downArrowFunction();
             break;
      }

   });

   functionupArraowFunction(a) {
       a = 'I change a, but a is not changed in keydown event';
       return a; // But now I return the changed variable so it will change if a variable is assigned where the function is called.
   }

   functiondownArrowFunction() {
       // Do something else
   }
});

Solution 2:

Do did you mean to have the console.log inside the keydown function?

I was able to get it to respond (as I would expect) like this:

$(function() { /* on page load load */var a = 38;
  var b = 0;
  $(document).bind('keydown',function(e){
    var key = e.which;
    if (a === key) {
      b=key;
    }
    console.log(a, b, key);
  });    
});

within the scope of the keydown function, a and b get set properly if you hit the up-arrow.

I suspect that what was happening was that your console.log happened on page load. Then after that, you initialized the binding and so you never saw the updated results.

Solution 3:

Try this

    $(document).on("keydown", function(e, key){
      var a = 38;
      var b = 0;
      if (e.which === a) {b = e.which};
      var key = (key === undefined ? b : a);
      returnconsole.log(a + " " + b + " " + key)
    });

Edit

yes but the problem is that within key down I can't use a and b because they get set to undefined and I have to initiate them in another part of my program – user3030188

Call your functions when the keydown event is triggered and maybe you could send the variable to the function instead of making it global. – L105

Yah that makes sense but what im wondering is whether I could pass in a or b as a case statement if I defined them in another part of the program would they get overridden why would it return undefined? – user3030188

Try this

functionkey(e, a, b, key) {
/* settings */var a = (a === undefined ? 38 : a);
   var b = (b === undefined ? 0 : b);
   if (e.which === a) {b = e.which};
   var key = (key === undefined ? b : a);
   returnconsole.log(a + " " + b + " " + key)
 };

$(document).on("keydown", key); /* `38` `38` `38` *//* `a`, `b` */
$(document).on("keydown", key({},undefined,undefined,undefined)); /* `38` `0` `0` *//* a`, `b`, or `n` */
$(document).on("keydown", function(n) {
  var n = 35;
  key({},37,n,undefined)
}); /* `37` `35` `35`*//* `n` */
$(document).on("keydown", function(n) {
  var n = 35;
  key({},n,n,undefined)
}); /* `35` `35` `35`*/