How to make characters jump using JavaScript-Front-end Q&A-php.cn

How to make characters jump using JavaScript

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Release： 2023-05-26 19:24:36

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With the continuous development of Internet technology, more and more people are beginning to learn programming languages. Among them, JavaScript is a very popular programming language and is widely used in web pages, games and other fields. In game development, character jumping is a very basic but important function. This article will introduce how to use JavaScript to implement character jumping.

1. Knowledge preparation

Before realizing the character jump, you need to master some basic knowledge. The first is HTML5 canvas technology and basic animation principles. HTML5 canvas is a new feature of HTML5 that can help us draw graphics and animations more flexibly. The second is the basics of JavaScript language, including event monitoring, timers and other knowledge.

2. Implementation Principle

The principle of realizing character jumping is very simple - the character jumps up and then falls down. Specifically, it can be achieved through the following steps:

Draw figures and ground: Draw figures and ground on the canvas.
Listen to key events: Listen to keyboard key events. When the jump key is pressed, the character will be triggered to jump.
Realize jumping animation: Use JavaScript timer to achieve jumping animation effect. Every once in a while, move the character's position upward a certain distance and change the character's vertical speed.
Implement the falling animation: When the character jumps to the highest point, the falling animation starts. Use JavaScript timer to implement falling animation effect. Every once in a while, move the character's position downward a certain distance and change the character's vertical speed.
Complete the jumping action: When the character falls to the ground, stop the jumping operation.

3. Code Implementation

Through the above steps, the character jumping function can be realized. The following is a simple JavaScript code implementation example:

<!DOCTYPE html>
<html>
<head>
    <title>JavaScript实现人物跳跃</title>
    <meta charset="UTF-8">
    <style>
        canvas{
            border: 1px solid #000;
        }
    </style>
</head>
<body>
    <canvas id="canvas" width="500" height="300"></canvas>
    <script>
        // 获取画布和上下文
        var canvas = document.getElementById("canvas");
        var context = canvas.getContext("2d");

        // 定义人物属性
        var x = 50;
        var y = 252;
        var width = 40;
        var height = 48;
        var vy = 0; // 初始垂直速度为0

        // 绘制人物和地面
        function draw(){
            context.clearRect(0, 0, canvas.width, canvas.height);

            context.fillStyle = "#000";
            context.fillRect(0, 300, 500, 3);

            context.fillStyle = "#FF0000";
            context.fillRect(x, y, width, height);
        }

        // 监听按键事件
        window.addEventListener("keydown", function(e){
            if(e.keyCode === 32 && y === 252){ // 当按下空格键且人物在地面时
                vy = -10; // 设置垂直速度为10
            }
        });

        // 实现跳跃动画和落下动画
        function update(){
            y += vy;
            vy += 0.5;

            if(y + height > 300){ // 当人物落到地面时
                y = 252;
                vy = 0;
            }
        }

        // 实现游戏循环
        function gameLoop(){
            draw();
            update();

            requestAnimationFrame(gameLoop);
        }

        gameLoop();
    </script>
</body>
</html>

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In the code, the characters and the ground are first drawn through the context. Then listen to the key event to determine whether the jump key is pressed, and set the character's initial vertical speed. Each time the jumping animation effect is achieved, the character's position is moved upward for a certain distance and the vertical speed of the character is changed at the same time. When the character jumps to the highest point, the falling animation begins. Every once in a while, move the character's position downward a certain distance and change the character's vertical speed. Finally, when the character hits the ground, stop jumping.

This article is only a simple implementation method for character jumping. In actual applications, the code needs to be further improved and optimized according to needs. At the same time, for beginners, only by mastering basic syntax and principles and accumulating practical experience can they be better applied in actual development.

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