How to draw polygons on an HTML5 canvas?

Question

I need to know how to draw polygons on a canvas. Without using jQuery or anything like that.

Answer 1

To make a simple hexagon without the need for a loop, Just use the beginPath() function. Make sure your canvas.getContext('2d') is the equal to ctx if not it will not work.

I also like to add a variable called times that I can use to scale the object if I need to.This what I don't need to change each number.

     // Times Variable 

     var times = 1;

    // Create a shape

    ctx.beginPath();
    ctx.moveTo(99*times, 0*times);
    ctx.lineTo(99*times, 0*times);
    ctx.lineTo(198*times, 50*times);
    ctx.lineTo(198*times, 148*times);
    ctx.lineTo(99*times, 198*times);
    ctx.lineTo(99*times, 198*times);
    ctx.lineTo(1*times, 148*times);
    ctx.lineTo(1*times,57*times);
    ctx.closePath();
    ctx.clip();
    ctx.stroke();

Answer 2

For the people looking for regular polygons:

function regPolyPath(r,p,ctx){ //Radius, #points, context
  //Azurethi was here!
  ctx.moveTo(r,0);
  for(i=0; i<p+1; i++){
    ctx.rotate(2*Math.PI/p);
    ctx.lineTo(r,0);
  }
  ctx.rotate(-2*Math.PI/p);
}

Use:

//Get canvas Context
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");

ctx.translate(60,60);    //Moves the origin to what is currently 60,60
//ctx.rotate(Rotation);  //Use this if you want the whole polygon rotated
regPolyPath(40,6,ctx);   //Hexagon with radius 40
//ctx.rotate(-Rotation); //remember to 'un-rotate' (or save and restore)
ctx.stroke();

Answer 3

In addition to @canvastag, use a while loop with shift I think is more concise:

var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');

var poly = [5, 5, 100, 50, 50, 100, 10, 90];

// copy array
var shape = poly.slice(0);

ctx.fillStyle = '#f00'
ctx.beginPath();
ctx.moveTo(shape.shift(), shape.shift());
while(shape.length) {
  ctx.lineTo(shape.shift(), shape.shift());
}
ctx.closePath();
ctx.fill();