Generate Animated Waves Using JavaScript And Canvas

Smoothly animated waves generated with JavaScript and HTML5 canvas. Ideal for creative page header.

How to use it:

Create an empty canvas element on the page.

<div class="canvas-wrap">
  <canvas id="canvas"></canvas>
</div>

The core JavaScript to generate animated waves.

(function(){
  "use strict";
  
  var cvs,ctx;
  //var nodes = 5;
  var waves = [];
  var waveHeight = 30;
  var colours = ["#f00","#0f0","#00f"]
  
  function init() {
    cvs = document.getElementById("canvas");
    ctx = cvs.getContext("2d");
    resizeCanvas(cvs);
    
    
    
    for (var i = 0; i < 3; i++) {
      var temp = new wave(colours[i],1,5);
    }
    setInterval(update,16);
    
  }
  function randomColour() {
    // body...
    var h = Math.round(Math.random()*360);
    return "hsl("+h+",100%,50%)";
  }
  function update(array) {
    // body...
    //ctx.clearRect(0, 0, cvs.width, cvs.height);
    var fill = window.getComputedStyle(document.querySelector(".header"),null).getPropertyValue("background-color");
    ctx.fillStyle = fill;
    ctx.globalCompositeOperation = "source-over";
    ctx.fillRect(0,0,cvs.width,cvs.height);
    ctx.globalCompositeOperation = "screen";
    for (var i = 0; i < waves.length; i++) {
      for (var j = 0; j < waves[i].nodes.length; j++) {
        bounce(waves[i].nodes[j]);
      }
      drawWave(waves[i]);
      //drawLine(waves[i].nodes);
      //drawNodes(waves[i].nodes);
    }
    ctx.globalCompositeOperation = "hue";
    ctx.fillStyle = fill;
    //ctx.fillRect(0,0,cvs.width,cvs.height);
  }
  function wave(colour,lambda,nodes) {
    // body...
    this.colour = colour;
    this.lambda = lambda;
    this.nodes = [];
    var tick = 1;
    for (var i = 0; i <= nodes+2; i++) {
      var temp = [(i-1)*cvs.width/nodes,0,Math.random()*200,.3];//this.speed*plusOrMinus
      this.nodes.push(temp);
      console.log(temp);
    }
    console.log(this.nodes);
    waves.push(this);
  }
  function bounce(node) {
    node[1] = waveHeight/2*Math.sin(node[2]/20)+cvs.height/2;
    node[2] = node[2] + node[3];
    
  }
  
  function drawWave (obj) {
    var diff = function(a,b) {
      return (b - a)/2 + a;
    }
    ctx.fillStyle = obj.colour;
    ctx.beginPath();
    ctx.moveTo(0,cvs.height);
    ctx.lineTo(obj.nodes[0][0],obj.nodes[0][1]);
    for (var i = 0; i < obj.nodes.length; i++) {
      if (obj.nodes[i+1]) {
        ctx.quadraticCurveTo(
          obj.nodes[i][0],obj.nodes[i][1],
          diff(obj.nodes[i][0],obj.nodes[i+1][0]),diff(obj.nodes[i][1],obj.nodes[i+1][1])
        );
      }else{
        ctx.lineTo(obj.nodes[i][0],obj.nodes[i][1]);
        ctx.lineTo(cvs.width,cvs.height);
      }
      
    }
    ctx.closePath();
    ctx.fill();
  }
  function drawNodes (array) {
    ctx.strokeStyle = "#888";
    for (var i = 0; i < array.length; i++) {
      ctx.beginPath();
      ctx.arc(array[i][0],array[i][1],4,0,2*Math.PI);
      ctx.closePath();
      ctx.stroke();
    }
    
  }
  function drawLine (array) {
    ctx.strokeStyle = "#888";
    for (var i = 0; i < array.length; i++) {
      if (array[i+1]) {
        ctx.lineTo(array[i+1][0],array[i+1][1]);
      }
    }
      ctx.stroke();
  }
  function resizeCanvas(canvas,width,height) {
    if (width && height) {
      canvas.width = width;
      canvas.height = height;
    } else {
      if (window.innerHeight > 1920) {
        canvas.width = window.innerWidth;
      }
      else {
        canvas.width = 1920;
      }
      
      canvas.height = waveHeight;
    }
    
  }
  
  document.addEventListener("DOMContentLoaded",init,false);
})();

Adjust the height of waves.

var waveHeight = 30;

Override the default colors.

var colours = ["#f00","#0f0","#00f"]