How to create canvas shapes

How to create canvas shapes

This is my code.I have to create canvas in a circle shape.
i am applying css in line code using canvas get context. i have tried but
nothing shows right.
if(shap=="circle")
{
var elementID = 'canvas' + $('canvas').length;
$('<canvas>').attr({
id: elementID
}).css({
width:1200,
height:600
}).appendTo('#work_area');
var canvas = document.getElementById(elementID);
var ctx = canvas.getContext('2d');
ctx.beginPath();
ctx.arc(100,75,50,0,2*Math.PI);
ctx.stroke();
}