How do you set an interval inside of an event?

Question

switch(event.keyCode)
{
//case(40):
// if(bottom < 406)
//{
// el.style.color = "black";
//el.style.top = 8 + top;
//}
//break;
// case(38):
// if(top !=0)
// {
// el.style.top = top - 8;
//}
// break;
case(37):
if(left > 0)
{
el.style.left = left - 8;
}
break;
case(39):
if(right < 512)
{
el.style.left = left +8;
}
break;
case(32):
//space
{
var intervalMain = setInterval(jump, 10);
}
}

I go into my jump function and try to clear this interval. I get the message that intervalMain is not defined. Why is that? intervalMain is a global variable.

Answer 1

The variable are in the local scope, so jump function cant see it.

Use anonymous function instead.
or declare intervalMain somewhere else where the jump function can see it

Answer 2

Just to further elaborate Taste's answer,

a short cure for you:

var intervalMain;

... codes...
... codes...
Your switch{
intervalMain = setInterval(); // no keyword var here
}
jump function{
clearInterval()
}

For enrichment, you need to understand an advanced JavaScript concept called Closure.
Here is David Carroll's pick
of 3 readings
from beginner to advanced:
https://www.sololearn.com/post/45261/?ref=app