92 lines
2.4 KiB
JavaScript
92 lines
2.4 KiB
JavaScript
(function() {
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var width, height, largeHeader, canvas, ctx, circles, target, animateHeader = true;
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// Main
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initHeader();
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addListeners();
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function initHeader() {
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width = window.innerWidth;
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height = window.innerHeight;
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target = {x: 0, y: height};
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largeHeader = document.getElementById('large-header');
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largeHeader.style.height = height+'px';
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canvas = document.getElementById('demo-canvas');
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canvas.width = width;
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canvas.height = height;
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ctx = canvas.getContext('2d');
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// create particles
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circles = [];
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for(var x = 0; x < width*0.5; x++) {
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var c = new Circle();
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circles.push(c);
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}
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animate();
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}
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// Event handling
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function addListeners() {
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window.addEventListener('scroll', scrollCheck);
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window.addEventListener('resize', resize);
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}
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function scrollCheck() {
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if(document.body.scrollTop > height) animateHeader = false;
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else animateHeader = true;
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}
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function resize() {
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width = window.innerWidth;
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height = window.innerHeight;
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largeHeader.style.height = height+'px';
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canvas.width = width;
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canvas.height = height;
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}
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function animate() {
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if(animateHeader) {
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ctx.clearRect(0,0,width,height);
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for(var i in circles) {
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circles[i].draw();
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}
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}
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requestAnimationFrame(animate);
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}
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// Canvas manipulation
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function Circle() {
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var _this = this;
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// constructor
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(function() {
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_this.pos = {};
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init();
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console.log(_this);
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})();
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function init() {
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_this.pos.x = Math.random()*width;
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_this.pos.y = height+Math.random()*100;
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_this.alpha = 0.1+Math.random()*0.3;
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_this.scale = 0.1+Math.random()*0.3;
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_this.velocity = Math.random();
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}
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this.draw = function() {
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if(_this.alpha <= 0) {
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init();
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}
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_this.pos.y -= _this.velocity;
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_this.alpha -= 0.0005;
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ctx.beginPath();
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ctx.arc(_this.pos.x, _this.pos.y, _this.scale*10, 0, 2 * Math.PI, false);
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ctx.fillStyle = 'rgba(255,255,255,'+ _this.alpha+')';
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ctx.fill();
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};
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}
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})(); |