JavaScript counter doesn't work

Question

I have made a JavaScript counter like this:

window.onload = function(){
    var target_date = new Date("Aug, 15, 2019").getTime();
}
var days, hours, minutes, seconds;
var countdown = document.getElementById("countdown");

setInterval(function (){
    var current_date = new Date().getTime();
    var seconds_left = (target_date - current_date) / 1000;

    days = parseInt(seconds_left / 86400);
    seconds_left = seconds_left % 86400;

    hours = parseInt(seconds_left / 3600);
    seconds_left = seconds_left % 3600;

    minutes = parseInt(seconds_left / 60);
    seconds = parseInt(seconds_left % 60);

    countdown.innerHTML= days + "d, " + hours + "h, " + minutes + "m, " + seconds + "s"; 
}, 1000); 

HTML:

<span id="countdown"></span>

The browser (Google Chorme) says:

Uncaught ReferenceError: target_date is not defined

Even if I remove the window.onload = function(){} , the will still not work. What have I done wrong?

Answer 1

It's all to do with variable scope . Here your target_date is defined within your window.onload , making it local to that function. If you want to use the variable outside of that function, declare it globally by moving it outside of the function:

var target_date; /* Declared globally. */
window.onload = function(){
    target_date = new Date("Aug, 15, 2019").getTime();
}

Answer 2

Change your first "}" to the end of the script

window.onload = function(){
            var target_date = new Date("Aug, 15, 2019").getTime();

        var days, hours, minutes, seconds;
        var countdown = document.getElementById("countdown");

        setInterval(function (){
            var current_date = new Date().getTime();
            var seconds_left = (target_date - current_date) / 1000;

            days = parseInt(seconds_left / 86400);
            seconds_left = seconds_left % 86400;

            hours = parseInt(seconds_left / 3600);
            seconds_left = seconds_left % 3600;

            minutes = parseInt(seconds_left / 60);
            seconds = parseInt(seconds_left % 60);

            countdown.innerHTML= days + "d, " + hours + "h, " + minutes + "m, " + seconds + "s"; 
        }, 1000); 
        }

Answer 3

Just move the curly bracket "}" of the window.onload to the end of the script

window.onload = function(){
    var target_date = new Date("Aug, 15, 2019").getTime();
    var days, hours, minutes, seconds;
    var countdown = document.getElementById("countdown");

    setInterval(function (){
        var current_date = new Date().getTime();
        var seconds_left = (target_date - current_date) / 1000;

        days = parseInt(seconds_left / 86400);
        seconds_left = seconds_left % 86400;
        hours = parseInt(seconds_left / 3600);
        seconds_left = seconds_left % 3600;

        minutes = parseInt(seconds_left / 60);
        seconds = parseInt(seconds_left % 60);

        countdown.innerHTML= days + "d, " + hours + "h, " + minutes + "m, " + seconds + "s"; 
    }, 1000);
}