I'm pretty new to coding and can't find out why this is outputting undefined:
var var0, list = [var0];
list[0] = true;
console.log(var0)
2 Answers
On line 1 you copy the value of var0 into the array.
On line 2 you replace the value in the array.
This doesn't have any effect on var0. That is just a variable that used to have a copy of the same value. It is not a reference.
8 Comments
Harry Landesburg
That makes sense, but how then can I store var0 inside that array so that it's value can be modified?
Quentin
You can't. JavaScript doesn't have explicit references.
VLAZ
@HarryLandesburg it's impossible. If you share what your overall goal is, we can probably advise how to approach it. Right now, it sounds like you probably just want to store your values in an object.
Harry Landesburg
Darn, I'd expect that to be possible :/
Harry Landesburg
@VLAZ I was attempting to check which arrow key is pressed making the code shorter than with if statements:
window.addEventListener('keydown', KD); var left, up, right, down, list = [left, up, right, down]; function KD(event) { let LA = 0; for (a = 37; a !== 41; a++) { if (event.keyCode == a) { list[LA] = true; } LA++ } LA = 0; } I guess I'll have to go back to using a bunch of if statements... |
You never use or define the value of var0.
list[0] = true;
This line replaces the value of the object in the 0 position (which is var0 because of the first line) to a boolean variable with the value "true".
What you mean to do is
var var0 = true, list = [var0];
console.log(list[0])
2 Comments
Harry Landesburg
I know I could assign it true already but I'm trying to store it inside an array then set the first variable to true
St.Nicholas
@HarryLandesburg - you can't because that's not how javascript works. You never pass a variable, just the value of the variable.
var0. What do you expect it to be?list[0]is the first item of the list. You don't have pointers and references here, just values -[var0]just creates an array[undefined], nothing more. There is no relation with the variable after the creation oflist.