Animation in html/css/js

I want to start an animation at a specific time or when the user scrolls on that page.

Code of the animation:

// Particles Animation (Hero Section)
document.addEventListener("DOMContentLoaded", function(event) {
  var canvas = document.getElementById('nokey'),
   can_w = parseInt(canvas.getAttribute('width')),
   can_h = parseInt(canvas.getAttribute('height')),
   ctx = canvas.getContext('2d');

// console.log(typeof can_w);

var ball = {
      x: 0,
      y: 0,
      vx: 0,
      vy: 0,
      r: 0,
      alpha: 1,
      phase: 0
   },
   ball_color = {
       r: 207,
       g: 255,
       b: 4
   },
   R = 2,
   balls = [],
   alpha_f = 0.03,
   alpha_phase = 0,
    
// Line
   link_line_width = 0.8,
   dis_limit = 260,
   add_mouse_point = true,
   mouse_in = false,
   mouse_ball = {
      x: 0,
      y: 0,
      vx: 0,
      vy: 0,
      r: 0,
      type: 'mouse'
   };

// Random speed
function getRandomSpeed(pos){
    var  min = -1,
       max = 1;
    switch(pos){
        case 'top':
            return [randomNumFrom(min, max), randomNumFrom(0.1, max)];
            break;
        case 'right':
            return [randomNumFrom(min, -0.1), randomNumFrom(min, max)];
            break;
        case 'bottom':
            return [randomNumFrom(min, max), randomNumFrom(min, -0.1)];
            break;
        case 'left':
            return [randomNumFrom(0.1, max), randomNumFrom(min, max)];
            break;
        default:
            return;
            break;
    }
}
function randomArrayItem(arr){
    return arr[Math.floor(Math.random() * arr.length)];
}
function randomNumFrom(min, max){
    return Math.random()*(max - min) + min;
}
console.log(randomNumFrom(0, 10));
// Random Ball
function getRandomBall(){
    var pos = randomArrayItem(['top', 'right', 'bottom', 'left']);
    switch(pos){
        case 'top':
            return {
                x: randomSidePos(can_w),
                y: -R,
                vx: getRandomSpeed('top')[0],
                vy: getRandomSpeed('top')[1],
                r: R,
                alpha: 1,
                phase: randomNumFrom(0, 10)
            }
            break;
        case 'right':
            return {
                x: can_w + R,
                y: randomSidePos(can_h),
                vx: getRandomSpeed('right')[0],
                vy: getRandomSpeed('right')[1],
                r: R,
                alpha: 1,
                phase: randomNumFrom(0, 10)
            }
            break;
        case 'bottom':
            return {
                x: randomSidePos(can_w),
                y: can_h + R,
                vx: getRandomSpeed('bottom')[0],
                vy: getRandomSpeed('bottom')[1],
                r: R,
                alpha: 1,
                phase: randomNumFrom(0, 10)
            }
            break;
        case 'left':
            return {
                x: -R,
                y: randomSidePos(can_h),
                vx: getRandomSpeed('left')[0],
                vy: getRandomSpeed('left')[1],
                r: R,
                alpha: 1,
                phase: randomNumFrom(0, 10)
            }
            break;
    }
}
function randomSidePos(length){
    return Math.ceil(Math.random() * length);
}

// Draw Ball
function renderBalls(){
    Array.prototype.forEach.call(balls, function(b){
       if(!b.hasOwnProperty('type')){
           ctx.fillStyle = 'rgba('+ball_color.r+','+ball_color.g+','+ball_color.b+','+b.alpha+')';
           ctx.beginPath();
           ctx.arc(b.x, b.y, R, 0, Math.PI*2, true);
           ctx.closePath();
           ctx.fill();
       }
    });
}

// Update balls
function updateBalls(){
    var new_balls = [];
    Array.prototype.forEach.call(balls, function(b){
        b.x += b.vx;
        b.y += b.vy;
        
        if(b.x > -(50) && b.x < (can_w+50) && b.y > -(50) && b.y < (can_h+50)){
           new_balls.push(b);
        }
        
        // alpha change
        b.phase += alpha_f;
        b.alpha = Math.abs(Math.cos(b.phase));
        // console.log(b.alpha);
    });
    
    balls = new_balls.slice(0);
}

// loop alpha
function loopAlphaInf(){
    
}

// Draw lines
function renderLines(){
    var fraction, alpha;
    for (var i = 0; i < balls.length; i++) {
        for (var j = i + 1; j < balls.length; j++) {
           
           fraction = getDisOf(balls[i], balls[j]) / dis_limit;
            
           if(fraction < 1){
               alpha = (1 - fraction).toString();

               ctx.strokeStyle = 'rgba(150,150,150,'+alpha+')';
               ctx.lineWidth = link_line_width;
               
               ctx.beginPath();
               ctx.moveTo(balls[i].x, balls[i].y);
               ctx.lineTo(balls[j].x, balls[j].y);
               ctx.stroke();
               ctx.closePath();
           }
        }
    }
}

// calculate distance between two points
function getDisOf(b1, b2){
    var  delta_x = Math.abs(b1.x - b2.x),
       delta_y = Math.abs(b1.y - b2.y);
    
    return Math.sqrt(delta_x*delta_x + delta_y*delta_y);
}

// add balls if there a little balls
function addBallIfy(){
    if(balls.length < 20){
        balls.push(getRandomBall());
    }
}

// Render
function render(){
    ctx.clearRect(0, 0, can_w, can_h);
    
    renderBalls();
    
    renderLines();
    
    updateBalls();
    
    addBallIfy();
    
    window.requestAnimationFrame(render);
}

// Init Balls
function initBalls(num){
    for(var i = 1; i <= num; i++){
        balls.push({
            x: randomSidePos(can_w),
            y: randomSidePos(can_h),
            vx: getRandomSpeed('top')[0],
            vy: getRandomSpeed('top')[1],
            r: R,
            alpha: 1,
            phase: randomNumFrom(0, 10)
        });
    }
}
// Init Canvas
function initCanvas(){
    canvas.setAttribute('width', window.innerWidth);
    canvas.setAttribute('height', window.innerHeight);
    
    can_w = parseInt(canvas.getAttribute('width'));
    can_h = parseInt(canvas.getAttribute('height'));
}
window.addEventListener('resize', function(e){
    console.log('Window Resize...');
    initCanvas();
});

function goMovie(){
    initCanvas();
    initBalls(30);
    window.requestAnimationFrame(render);
}
goMovie();

// Mouse effect
canvas.addEventListener('mouseenter', function(){
    console.log('mouseenter');
    mouse_in = true;
    balls.push(mouse_ball);
});
canvas.addEventListener('mouseleave', function(){
    console.log('mouseleave');
    mouse_in = false;
    var new_balls = [];
    Array.prototype.forEach.call(balls, function(b){
        if(!b.hasOwnProperty('type')){
            new_balls.push(b);
        }
    });
    balls = new_balls.slice(0);
});
canvas.addEventListener('mousemove', function(e){
    var e = e || window.event;
    mouse_ball.x = e.pageX;
    mouse_ball.y = e.pageY;
    // console.log(mouse_ball);
});
});
document.addEventListener("DOMContentLoaded", function(event) {

  let getWindowDimensions = {
  width: 0,
  height: 0
};

const handleResize = () => {
    getWindowDimensions.width = window.innerWidth;
    getWindowDimensions.height = window.innerHeight;
  };

window.addEventListener('resize', handleResize());


function myFunc() { document.getElementById("makeWindowHeight").style.height = `${getWindowDimensions.height}px`;
}
 
myFunc();

console.log(getWindowDimensions);
});
canvas{
   z-index: -1;
    position: fixed;
    background-color: transparent;
    height: 100%;
    padding: 0;
    margin:0;
}
<body>
    <canvas id="nokey"></canvas>
  </body>

Right now, my output looks like this:

enter image description here

As you can see the animation is displayed on this page, and I do not want that. I do not want the animation to be on the homepage or the hero section. When the user scrolls down to another section, the animation should be there. In short, is there a way to not make the animation on the page I showed in the picture, but when you scroll down, the animation becomes visible? Any suggestions?

Is there a js code that would allow the animation to appear after a specific time or after the page I sent in the picture?

2 thoughts on “Animation in html/css/js”

  1. Use the IntersectionObserver API to trigger a callback that begins the animation when the page section scrolls into view and which ends the animation when it scrolls out of view.

    let options = {
      root: document.querySelector('#animated-section'),
      rootMargin: '0px',
      threshold: 1.0
    }
    
    let observer = new IntersectionObserver(entries => {
      entries[0].intersectionRatio <= 0 ? animationStop() : animationStart()
    }, options);
    
    Reply
  2. You might be able to accomplish this in CSS and assigning id’s for a fixed height within your tag.

    <html>
    <head>
    <style>
        #grad1R {
          height: 500px;
          background-image: linear-gradient(to left, rgba(89,198,241), rgba(255,255,255));
        }
        
        #grad1L {
          height: 400px;
          background-image: linear-gradient(to left, rgba(89,198,241), rgba(255,255,255));
        }
        
        #grad2R {
            height: 300px;
            background-image: linear-gradient(to right, rgba(19,117,188), rgba(255,255,255));
            
        #grad2R {
            height: 200px;
            background-image: linear-gradient(to left, rgba(19,117,188), rgba(255,255,255));
    </style>
    </head>
    <body>
    <header id="grad1R">
    <h1>Linear Gradient - Transparency</h1>
        <p>To add transparency, we use the rgba function to define the color stops. The last parameter in the rgba() function can be a value from 0 to 1, and it defines the transparency of the color.</p>
    </header>
    <header id="grad1L">
        <p>To add transparency, we use the rgba() function to define the color stops. The last parameter in the rgba() function can be a value from 0 to 1, and it defines the transparency of the color: 0 indicates full transparency, 1 indicates full color (no transparency).</p>
    </header>
    <header id="grad2L">
        <p>To add transparency, we use the rgba() function to define the color stops. The last parameter in the rgba() function can be a value from 0 to 1, and it defines the transparency of the color: 0 indicates full transparency, 1 indicates full color (no transparency).</p>
    </header>
    <header id="grad2R">
        <p>To add transparency, we use the rgba() function to define the color stops. The last parameter in the rgba() function can be a value from 0 to 1, and it defines the transparency of the color: 0 indicates full transparency, 1 indicates full color (no transparency).</p>
    </header>
    </body>
    </html>
    

    I’m learning how to do gradients with CSS in w3Schools TryIt Editor, but let me know if this helps. If you are testing in multiple devices though, this may not be "responsive" and respect the device dimensions of your users.

    Have you used GetBootstrap.com yet?

    Reply

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