How to I Create a Simple Countdown Timer for 10 Minutes Without setInterval()

I want to create a simple countdown timer for 10 minutes. I have figured out how to do this for the most part but with setInterval() it seems to stop with 2 seconds left every time. I have heard that setInterval() can be very unreliable but I don't know what else to do.

I set the timer to 1 minute and the seconds reset to 3 instead of 59 for time-saving purposes with running the code.

const value = document.querySelector("#time");
const startBtn = document.querySelector("#btn-start")
const resetBtn = document.querySelector("#btn-reset");

startBtn.addEventListener('click', function(){
    var minute = 1;
    var sec = 3;
    setInterval(function(){
        value.innerHTML = minute + ":" + sec;
        sec--;
        if(sec < 0){
            minute--;
            sec = 3;
        }
        if(sec <=9){
            sec = "0" + sec;
        }
        if(sec == 0 && minute == 0){
            alert("DONE!");
            location.reload();
        }
    }, 1000);
});
resetBtn.addEventListener('click', function(){
        location.reload();
})
#main{
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    height: 100%;
}
.container{
    position: relative;
    margin-top: 5%;
}
#title{
    display: block;
    font-family: 'Roboto', sans-serif;
    font-size: 50px;
    font-weight: 600;
    color:rgba(0, 0, 0, 0.83);
    margin: 20px auto;
    padding: 0;

}
#time{
    display: block;
    font-family: 'Roboto', sans-serif;
    font-size: 70px;
    text-align: center;
    margin: 20px auto 50px auto;
}
.function-buttons{
    position: relative;
    display: flex;
    flex-direction: row;
    justify-content: center;
    align-items: center;
}
.reset-btn{
    display: block;
    font-family: 'Roboto', sans-serif;
    font-size: 25px;
    width: 150px;
    background: #eee;
    margin: 0 10px;
    padding: 10px 30px;
    text-align: center;
    border-radius: 5px;
    border: none;
    outline: none;
    transition: .4s ease-in-out;
    cursor: pointer;    
}
.reset-btn:hover{
    background: red;
    color: #fff;
}
.start-btn{
    display: block;
    font-family: 'Roboto', sans-serif;
    font-size: 25px;
    width: 150px;
    background: #eee;
    margin: 0 10px;
    padding: 10px 30px;
    text-align: center;
    border-radius: 5px;
    border: none;
    outline: none;
    transition: .4s ease-in-out;
    cursor: pointer;
}
.start-btn:hover{
    background: #0096ff;
    color: #fff;
}
<!DOCTYPE html>
<html>
    <head>
        <title>Countdown Timer</title>
        <link href="" rel="stylesheet">
        <link rel="stylesheet" type="text/css" href="main.css">
    </head>
    <body>
        <header id="header">
            <div class="logo">
                <h1 id="title">
                    Countdown Timer
                </h1>
            </div>
        </header>
        <main id="main">
            <div class="container">
                <div class="countdown-container">
                    <h1 id="title">
                        10 Minute Timer
                    </h1>
                    <span id="time">10:00</span>
                </div>
                <div class="function-buttons">
                    <button class="reset-btn" id="btn-reset">
                        Reset
                    </button>
                    <button class="start-btn" id="btn-start">
                        Start
                    </button>
                </div>
            </div>
        </main>
        <script src="app.js"></script>
    </body>
</html>
2

1 Answer

setInterval is the best way to do what you want. It is printing "Done" with 2 second left because you are sec-- just after updating your DOM.

To solve the problem, you can just do sec-- and you DOM update at the end of your interval function like so

const value = document.querySelector("#time");
const startBtn = document.querySelector("#btn-start")
const resetBtn = document.querySelector("#btn-reset");

startBtn.addEventListener('click', function(){
    var minute = 1;
    var sec = 3;
    setInterval(function(){
        if(sec < 0){
            minute--;
            sec = 3;
        }
        if(sec <=9){
            sec = "0" + sec;
        }
        if(sec == 0 && minute == 0){
            alert("DONE!");
            location.reload();
        }
        value.innerHTML = minute + ":" + sec;
        sec--;
    }, 1000);
});
resetBtn.addEventListener('click', function(){
        location.reload();
})
#main{
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    height: 100%;
}
.container{
    position: relative;
    margin-top: 5%;
}
#title{
    display: block;
    font-family: 'Roboto', sans-serif;
    font-size: 50px;
    font-weight: 600;
    color:rgba(0, 0, 0, 0.83);
    margin: 20px auto;
    padding: 0;

}
#time{
    display: block;
    font-family: 'Roboto', sans-serif;
    font-size: 70px;
    text-align: center;
    margin: 20px auto 50px auto;
}
.function-buttons{
    position: relative;
    display: flex;
    flex-direction: row;
    justify-content: center;
    align-items: center;
}
.reset-btn{
    display: block;
    font-family: 'Roboto', sans-serif;
    font-size: 25px;
    width: 150px;
    background: #eee;
    margin: 0 10px;
    padding: 10px 30px;
    text-align: center;
    border-radius: 5px;
    border: none;
    outline: none;
    transition: .4s ease-in-out;
    cursor: pointer;    
}
.reset-btn:hover{
    background: red;
    color: #fff;
}
.start-btn{
    display: block;
    font-family: 'Roboto', sans-serif;
    font-size: 25px;
    width: 150px;
    background: #eee;
    margin: 0 10px;
    padding: 10px 30px;
    text-align: center;
    border-radius: 5px;
    border: none;
    outline: none;
    transition: .4s ease-in-out;
    cursor: pointer;
}
.start-btn:hover{
    background: #0096ff;
    color: #fff;
}
<!DOCTYPE html>
<html>
    <head>
        <title>Countdown Timer</title>
        <link href="" rel="stylesheet">
        <link rel="stylesheet" type="text/css" href="main.css">
    </head>
    <body>
        <header id="header">
            <div class="logo">
                <h1 id="title">
                    Countdown Timer
                </h1>
            </div>
        </header>
        <main id="main">
            <div class="container">
                <div class="countdown-container">
                    <h1 id="title">
                        10 Minute Timer
                    </h1>
                    <span id="time">10:00</span>
                </div>
                <div class="function-buttons">
                    <button class="reset-btn" id="btn-reset">
                        Reset
                    </button>
                    <button class="start-btn" id="btn-start">
                        Start
                    </button>
                </div>
            </div>
        </main>
        <script src="app.js"></script>
    </body>
</html>

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Chloe Bennett

Chloe Bennett

Culture, Media & Entertainment Columnist

Chloe Bennett explores the intersection of pop culture, streaming entertainment, digital trends, and contemporary lifestyle. Her weekly commentary reaches thousands of culture enthusiasts.

Share this article
Twitter Facebook Pinterest