Run if statement only one time inside scroll event

Question

I have this code, I tried to execute the if statement only one time. So the user will get only one alert show when getting to the middle of the page, after skipping the alert and keep scrolling he shouldn't get the alert again. so I added this PassedValue boolean variable but it doesn't get changed to true when the alert is shown.

 $f = $.noConflict(); $f(document).ready(function() { $f(window).scroll(function() { var scrollAmount = $f(window).scrollTop(); var documentHeight = $f(document).height(); var scrollPercent = (scrollAmount / documentHeight) * 100; var PassedValue = false; //$(".3amal").append(scrollPercent); if (scrollAmount > documentHeight * 0.3 && !PassedValue) { alert('the user scrolled once!'); PassedValue = true; } else { //alert('Nothing done nothing to save'); } }); });

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Answer 1

You can create an external variable and then check it in the if statement:

// somewhere outside your handler/function
let reviewed = false;

// inside
if(scrollAmount > documentHeight*0.3 && !PassedValue && !reviewed) {
  reviewed = true;
  // your logic here
}

Answer 2

The PassedValue should be out of the scroll event method scope. Everytime the code calls the scroll event, the var passedValue is created as it is inside the scroll event. If you make it as global variable, it should work.

$f = $.noConflict();

// Moved passedValue to a global variable
var PassedValue=false;

$f(document).ready(function() {
 $f(window).scroll(function() {
 var scrollAmount = $f(window).scrollTop();
 var documentHeight = $f(document).height();
 var scrollPercent = (scrollAmount / documentHeight) * 100;

 //$(".3amal").append(scrollPercent);
  if(scrollAmount > documentHeight*0.3 && !PassedValue){
alert('the user scrolled once!');
PassedValue=true;
  }else{
  //alert('Nothing done nothing to save');
  }
});
});