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JavaScript implements automatic scrolling of text strips

PHPz

May 10, 2023 am 09:15 AM

JavaScript is a very popular programming language. It is mainly used for web development and can implement a variety of rich functions. Today, we will introduce how to use JavaScript to implement the automatic scrolling function of the note to better meet user needs.

1. Requirements Analysis

The function we need to implement is a dynamic text strip that automatically scrolls so that more content can be presented on the page without affecting the page layout. The specific implementation needs to consider the following aspects:

The text content of the note: We need to define an area on the page to display the text content of the note, and the text content needs to be loaded dynamically.
Scrolling speed of the note: We hope to be able to adjust the scrolling speed of the note to better suit different user needs.
Scrolling direction of the text bar: We need to consider the direction in which the text bar scrolls, whether it is scrolling left, right, up or down.
The stay time of the note: We need to consider the time the note stays when it scrolls to the end, so that the user has enough time to read the content of the note.

2. Solution design

Based on the above demand analysis, we can design the following solution:

Create an HTML element to display the text of the note content. We can use a div element and set the appropriate CSS styles for it so that it displays on the page in the appropriate position.
Use JavaScript to dynamically load the text content of the note. We can use the XMLHttpRequest object to initiate a request to the server, obtain the text content of the note, and set it into an HTML element.
Set the scrolling speed of the note through JavaScript. We can use the setInterval function to regularly calculate the position offset of the text bar and update the position information of the HTML element to produce a scrolling effect.
Set the scrolling direction of the note through JavaScript. We can define a direction variable to record the scrolling direction of the note, and change the position information of the note based on the value of the variable.
Set the stay time of the note through JavaScript. We can use the setTimeout function to set a dwell time when the note scrolls to the end, so that the user has enough time to read the content of the note.

3. Code implementation

Based on the above scheme design, we can write the following code:

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>JavaScript实现字条自动滚动</title>
<style>
#box {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-50%);
    font-size: 20px;
    color: #fff;
    background-color: #000;
    padding: 10px;
}

</style>
</head>
<body onLoad="init()">
    <div id="box"></div>
    <script>
    var direction = 1; // 1代表向左滚动，-1代表向右滚动
    var speed = 50; // 滚动速度，单位是像素/秒
    var pauseTime = 5000; // 停留时间，单位是毫秒
    var timer = null;
    var p1 = 0;
    var p2 = 0;

    function init() {
        loadText();
        setInterval(scrollText, 20);
    }

    function loadText() {
        var xhttp = new XMLHttpRequest();
        xhttp.onreadystatechange = function() {
            if (this.readyState == 4 && this.status == 200) {
                document.getElementById("box").innerHTML = this.responseText;
                p2 = document.getElementById("box").offsetWidth + 10;
            }
        };
        xhttp.open("GET", "text.txt", true);
        xhttp.send();
    }

    function scrollText() {
        var box = document.getElementById("box");

        if (direction == 1) {
            p1 += speed / 50;
            if (p1 > p2) {
                direction = -1;
                setTimeout(function(){direction = 1;}, pauseTime);
            }
        } else {
            p1 -= speed / 50;
            if (p1 < -box.offsetWidth) {
                direction = 1;
                setTimeout(function(){direction = -1;}, pauseTime);
            }
        }

        box.style.left = p1 + "px";
    }
    </script>
</body>
</html>

Code description:

In Define a div element with the id "box" in the HTML page to display the text content of the note. And set some CSS styles and some JavaScript events for it to initialize the page content when the page loads.
Define some variables in JavaScript to save the scrolling direction, scrolling speed, dwell time, timer and other related information of the note.
Use the XMLHttpRequest object to request the server to obtain the text content of the note and set it into the HTML element.
Use the setInterval function to regularly calculate and update the position information of HTML elements to produce a scrolling effect. During the calculation process, the position information of the HTML element is changed according to the value of the direction variable.
When scrolling to the end, use the setTimeout function to wait for a period of time so that the user has enough time to read the content of the note.

4. Summary

This article introduces how to use JavaScript to realize the automatic scrolling function of the note. Through analysis of requirements, we designed a relatively complete solution and explained it through actual code demonstrations. I hope that through the introduction of this article, you can have a deeper understanding of JavaScript applications and be able to better meet user needs in your development work.

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