Function to draw a rectangle on a canvas element

gistfile1.js

function clearCanvas(context, canvas) {
  context.clearRect(0, 0, canvas.width, canvas.height);
  var w = canvas.width;
  canvas.width = 1;
  canvas.width = w;
}

function highlightRoom(x, y, h, w){
  var can = document.getElementsByTagName('canvas')[0];
  var ctx = can.getContext('2d');
  clearCanvas(ctx, can);
  ctx.strokeStyle = '#f00';
  ctx.lineWidth = 5;
  ctx.lineJoin = 'round';
  ctx.strokeRect(x,y,h,w);
}