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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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Adding Classes

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About the <head>

In CodePen, whatever you write in the HTML editor is what goes within the <body> tags in a basic HTML5 template. If you need things in the <head> of the document, put that code here.

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Insecure Resource

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CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

We offer two popular choices: Autoprefixer (which processes your CSS server-side) and -prefix-free (which applies prefixes via a script, client-side).

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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HTML 

              
                <body>
  <canvas class='canvas' id='bezier'></canvas>
</body>
!

CSS 

              
                body {
  background-color:#000;
  overflow: hidden;
}

body,
html {
  height: 100%;
  width: 100%;
  margin: 0;
  padding: 0;
 }

.canvas{
  position:absolute;
  margin:auto;
  top:0;
  bottom:0;
  left:0;
  right:0;
  /*width : 500px;
  height : 300px;*/
}
!

JS 

              
                var canvas;
var ctx;
var xa = 275;
var ya = 340;
var xca = 25;
var yca = 65;
var xb = 375;
var yb = 50;
var xcb = 507;
var ycb = 165;
var WIDTH = 700;
var HEIGHT = 400;
var dragok = false;
var pointA = false;
var pointControlA = false;
var pointB = false;
var pointControlB = false;

function rect(x,y,w,h) {
 ctx.beginPath();
 ctx.rect(x,y,w,h);
 ctx.closePath();
 ctx.fill();
}

function clear() {
 ctx.clearRect(0, 0, WIDTH, HEIGHT);
}

function init() {
 canvas = document.getElementById("bezier");
 ctx = canvas.getContext("2d");
 canvas.setAttribute('width', WIDTH);
 canvas.setAttribute('height', HEIGHT);
 return setInterval(draw, 10);
}

function draw() {
 clear();
 ctx.fillStyle = "#FAF7F8";
 rect(0,0,WIDTH,HEIGHT);
 ctx.fillStyle = "#444444";
 rect(xa - 5, ya - 5, 10, 10);
 rect(xb - 5, yb - 5, 10, 10);
 ctx.fillStyle = "#0095cd"; 
 rect(xca - 5, yca - 5, 10, 10);
 rect(xcb - 5, ycb - 5, 10, 10);
 
  lerp(xa, ya, xca, yca);
  lerp(xb, yb, xcb, ycb);
  
  bezier();
}

function lerp(pAx, pAy, pBx, pBy){
  ctx.strokeStyle = "#0095cd";
  ctx.beginPath();
  ctx.moveTo(pAx,pAy);
  ctx.lineTo(pBx,pBy);
  ctx.stroke();
}

function bezier(){
  ctx.strokeStyle ="#000";
  ctx.beginPath();
  ctx.moveTo(xa,ya);
  ctx.bezierCurveTo(xca,yca,xcb,ycb,xb,yb);
  ctx.stroke();
}
function myMove(e){
 if (dragok){
   if (pointA){
     xa = e.pageX - canvas.offsetLeft;
     ya = e.pageY - canvas.offsetTop;
   } else if (pointB){
     xb = e.pageX - canvas.offsetLeft;
     yb = e.pageY - canvas.offsetTop;
   } else if (pointControlA){
     xca = e.pageX - canvas.offsetLeft;
     yca = e.pageY - canvas.offsetTop;
   } else if (pointControlB){
     xcb = e.pageX - canvas.offsetLeft;
     ycb = e.pageY - canvas.offsetTop;
   }
 }
}

function myDown(e){
  /*var debugX = e.pageX - 5 - canvas.offsetLeft;
  var debugY = e.pageY -5 - canvas.offsetTop;
  console.log('x '+debugX+' y '+debugY);*/
 if (e.pageX < xa + 5 + canvas.offsetLeft && e.pageX > xa - 5 +
 canvas.offsetLeft && e.pageY < ya + 5 + canvas.offsetTop &&
 e.pageY > ya -5 + canvas.offsetTop){
  xa = e.pageX - canvas.offsetLeft;
  ya = e.pageY - canvas.offsetTop;
  dragok = true;
  pointA = true;
  canvas.onmousemove = myMove;
 } else if (e.pageX < xb + 5 + canvas.offsetLeft && e.pageX > xb - 5 +
 canvas.offsetLeft && e.pageY < yb + 5 + canvas.offsetTop &&
 e.pageY > yb -5 + canvas.offsetTop){
  xb = e.pageX - canvas.offsetLeft;
  yb = e.pageY - canvas.offsetTop;
  dragok = true;
  pointB = true;
  canvas.onmousemove = myMove;
 } else if (e.pageX < xca + 5 + canvas.offsetLeft && e.pageX > xca - 5 +
 canvas.offsetLeft && e.pageY < yca + 5 + canvas.offsetTop &&
 e.pageY > yca -5 + canvas.offsetTop){
  xca = e.pageX - canvas.offsetLeft;
  yca = e.pageY - canvas.offsetTop;
  dragok = true;
  pointControlA = true;
  canvas.onmousemove = myMove;
 } else if (e.pageX < xcb + 5 + canvas.offsetLeft && e.pageX > xcb - 5 +
 canvas.offsetLeft && e.pageY < ycb + 5 + canvas.offsetTop &&
 e.pageY > ycb -5 + canvas.offsetTop){
  xcb = e.pageX - canvas.offsetLeft;
  ycb = e.pageY - canvas.offsetTop;
  dragok = true;
  pointControlB = true;
  canvas.onmousemove = myMove;
 }
}

function myUp(){
 dragok = false;
 pointA = false;
 pointControlA = false;
 pointB = false;
 pointControlB = false;
 canvas.onmousemove = null;
}

init();
canvas.onmousedown = myDown;
canvas.onmouseup = myUp;
!
999px

Console