<canvas width="600" height="400" > </canvas>
<script>
function dibujarRectangulo(x,y,altura,color) {
var base = Math.round(Math.random()*90)
var pantalla = document.querySelector("canvas");
var pincel = pantalla.getContext("2d");
pincel.fillStyle = color;
pincel.fillRect(x,y,altura,base);
pincel.strokeStyle = "black";
pincel.strokeRect(x,y,altura,base);
}
dibujarRectangulo(50,50,100,"red")
</script>