If you want run once after page load try this:
var onlyOnce = true;
window.onscroll = function() {tourstart()};
function tourstart() {
if (document.body.scrollTop > 50 && onlyOnce) {
onlyOnce = false;
introJs().start();
}
}
But if you want run once for user(/browser), you can use the cookies, here an other stackoverflow solution for use the cookies but copy/paste the functions here:
The code change in this way :
var onlyOnce = readCookie("once");
window.onscroll = function() {tourstart()};
function tourstart() {
if (document.body.scrollTop > 50 && onlyOnce!="true") {
createCookie("once", "true", 10); // It expires in 10 days for example
introJs().start();
}
}
function createCookie(name,value,days) {
if (days) {
var date = new Date();
date.setTime(date.getTime()+(days*24*60*60*1000));
var expires = "; expires="+date.toGMTString();
}
else var expires = "";
document.cookie = name+"="+value+expires+"; path=/";
}
function readCookie(name) {
var nameEQ = name + "=";
var ca = document.cookie.split(';');
for(var i=0;i < ca.length;i++) {
var c = ca[i];
while (c.charAt(0)==' ') c = c.substring(1,c.length);
if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
}
return null;
}