Javascript - How to include javascript session?

Question

Currently working on a JavaScript on a SharePoint home page.

The script below will popup a window that shows a message: "Welcome to new page."

However, it is going to be annoying if it appears every single time user go to the page.

Is there a way to show the popup only once for per user each session?

<script language="javascript" type="text/javascript"> 
ExecuteOrDelayUntilScriptLoaded(yourFunction, 'SP.js'); 
function CloseCallback()
{
SP.UI.ModalDialog.commonModalDialogClose(SP.UI.DialogResult.Cancel);
} 
function yourFunction() 
{ SP.UI.ModalDialog.showWaitScreenWithNoClose('Welcome to the new site'); 
setTimeout(function() { CloseCallback(); }, 2000); }
 _spBodyOnLoadFunctionNames.push("yourFunction()"); </script>   

Answer 1

You can make use of sessionStorage to store data per browser session.

Do try and modify the below code:

<script language="javascript" type="text/javascript"> 

ExecuteOrDelayUntilScriptLoaded(yourFunction, 'SP.js'); 

function CloseCallback()
{
    SP.UI.ModalDialog.commonModalDialogClose(SP.UI.DialogResult.Cancel);
} 

function yourFunction() 
{   
    //check if session storage exists and also check if session storage contains an item with `some_key`
    if(window.sessionStorage && window.sessionStorage.getItem("some_key")){ 
        console.log("already loaded");
    }else{
        //set value in session storage
        window.sessionStorage.setItem("some_key", "first_load_screen");
        SP.UI.ModalDialog.showWaitScreenWithNoClose('Welcome to the new site'); 
        setTimeout(function() { CloseCallback(); }, 2000);  
    }
}

_spBodyOnLoadFunctionNames.push("yourFunction"); 

</script>