Javascript setTimout question

[TheCrock]

I am following the excellent book Foundation Game Design with HTML5 and Javascript.

I have a piece of code, which works but i'm not sure why.



function destroyAlien(alien)
{
//Change the alien's state and update the object
alien.state = alien.EXPLODED;

alien.update();

//Remove the alien after 1 second
setTimeout(removeAlien, 1000);

function removeAlien()
{
removeObject(alien, aliens);
removeObject(alien, sprites);
}


As you can see it is a function which uses setTimout to call another function. It only calls removeAlien function when it is inside the main function. If I move callAlien function out of the main function it does not work. I am puzzled as to why this is.

Can any sage member here tell me why this is?
Thanks in advance
Crock

TheCrock

 

Posts: 2

Joined: 12 Nov 2020, 16:02

•  

 

[b10b]

Javascript "scope".  When running in "strict" mode a function can only access members of itself.  To access functions or variables outside of itself involves other approaches.  Perhaps "Foundation Game Design" covers this topic?

https://www.w3schools.com/js/js_scope.asp

 

[TheCrock]

Now I understand b10b 

Thank you for the reply and explanation with link.Most kind.

Very early in the book there was indeed a paragraph on scope which I had forgotten. I ran a search for scope through the pdf and found it.

Thanks again.