I have a global Variable.
var w = 4;
and a function:
function do() {
width = w;
//make something
}
and now i want to change the variable w to 8 with a button.
<input type="button" onclick="do(w = 8;)" value="set 8">
that the function can work with w = 8 and forget the old w = 4!
You need to put w in the proper scope:
var w = 4;
function do(width) {
w = width;
// ...
}
And then pass an argument to your function:
<input type="button" onclick="do(8)" value="set 8">
I'm afraid that your code is wrong, almost from start to finish. You really do need to read a book on the basic syntax of using Javscript.
That said, this will do what you asked for:
var w = 4; // Bad idea to have a global variable. It is also unused.
function do(w) { // You pass a parameter here.
var width = w; // no need for this because now you have a 'w'
//make something
}
<input type="button" onclick="do(8)" value="set 8"> <!-- the value does nothing here -->
