How to prevent function from beeing called multiple times in row ?

[Martin C++]

I have a function that changes slides, I have created a pause and resume functions for it, but when the user presses resume button multiple times, then multiple instances of the script is beeing run and the images change too fast. I need to prevent this from happening.

This is my script in case it might help to make my sentences above to sound less confusing.

/*var image1 = new Image();
image1.src="images/4.jpg";
var image2 = new Image();
image2.src = "images/5.jpg";

var i = 2;

function change(){
i = ((i<=2) ? i : 1);
document.images.slide.src = eval("image"+i+".src");
i++;
setTimeout("change()", 1000);

}
change();
*/

function set_var(){

	/*Change these values according to your needs*/
	if(typeof(step) == "undefined"){
		newElem = document.createElement('img');
		linkPause = document.createElement('a');	
		namePause = document.createTextNode("Pause");
		linkPause.appendChild(namePause);
		linkPause.setAttribute("onclick", "pause()");
		linkPause.style.position = "absolute";
		
		linkResume = document.createElement('a');
		nameResume = document.createTextNode("Resume");
		linkResume.appendChild(nameResume);
		linkResume.setAttribute("onclick", "resume()");
		linkPause.style.position = "absolute";
		linkResume.style.position = "absolute";
		linkResume.style.left = "60px";

		
		slideDiv = document.getElementById('slideshow'); //Name of the division that the slideshow will occur on
		slideDiv.appendChild(newElem);
		slideDiv.appendChild(linkPause);
		slideDiv.appendChild(linkResume);

		extention = "jpg";
		imgPath = "images/"
		numImg = 2; //How many images you want to add in slideshow. Slides start from 1 and are limited with this variable
	}
		return true;

}

function slide(){

	if(set_var()) {
		((typeof(step) != "undefined" && step<=numImg) ? step = step : step = 1);
		newElem.src = imgPath + step + "." + extention;
		step++;
		t = setTimeout("slide()", 5000);
	}
}

function resume(){
	t = setTimeout("slide()",5000);
}

function pause(){
	clearTimeout(t);

}

[Martin C++]

Okay I managed to come out with something, but I m getting an error "boolean is not a function" when I try to resume after pausing the script.

Those are my new updated resume() and pause() functions.

function resume(){
	alert("Trying to resume");
	((typeof(resume) == "undefined") ? resume = true : "");
	alert("Trying to resume");
	if(resume == false){
		alert("evaluated true");
		t = setTimeout("slide()",2000);
		resume = true;
		alert(resume);
	}
}

function pause(){
	resume = false;
	clearTimeout(t);
}

[Martin C++]

I had accidentally named the variable with same name as the function, everything works now. Problem solved.