ReferenceError SetInterval not defined [closed]

Question

Nearly all the SetInterval errors I've seen here on StackOverflow are due to passing a function name as a "string," but maybe I am still missing some sort of variable scope problem. Please advise!

I'm creating a slideshow with pause and play capabilities. When playing, I want the slides to advance every 3 seconds. But the SetInterval to launch the NextSlide function is failing after executing once.

I've tried it as...

SetInterval("nextSlide()", 3000)
SetInterval(nextSlide(), 3000)
var t = SetInterval(nextSlide(), 3000)
var t = SetInterval(function(){nextSlide(), 3000)

... with failure every time. What am I missing here?

var slide_1 = "slide_1";
var slide_2 = "slide_2";
var slideNum = 0;
var odd = true;
var totalMax = 6;
var busy = false;

var allSlides = new Array();
allSlides[0] = "test_01";
allSlides[1] = "test_02";
allSlides[2] = "test_03";
allSlides[3] = "test_04";
allSlides[4] = "test_05";
allSlides[5] = "test_06";
allSlides[6] = "test_07";

function PlaySlide(){
var t = SetInterval(nextSlide(),3000)
document.getElementById("play").style.visibility = "hidden";
document.getElementById("pause").style.visibility = "visible";
}

function nextSlide(){
if(slideNum < totalMax && !busy){
busy = true
document.getElementById("loading").style.zIndex = 4;
slideNum = slideNum + 1
var slide = allSlides[slideNum]
var link = "https://dl.dropboxusercontent.com/u/..." + slide + ".jpg"
odd = !odd
if(odd){document.getElementById(slide_1).src = link} //which <img>.onLoad lauches a fadeIn()
else{document.getElementById(slide_2).src = link}
}
}

Answer 1

var t = SetInterval(nextSlide(),3000)
        ^                    ^^

You have 2 problems

There is no SetInterval, the s is lowercase. Second, you are calling the function nextSlide(), not assigning it

var t = window.setInterval(nextSlide, 3000);