drawimage() not working in js

I want to draw an image in javascript and i dont know why its not working here is the code.

     var canvas = document.getElementById('canvas');
     var ctx = canvas.getContext('2d');
     canvas.width = 640;
     canvas.height = 480;
     var playerimg = new Image();

     function setup(){
     render();
     }
     function render()
     {
     playerimg.onload = drawcharacter();
     }
     function drawcharacter(){
     ctx.drawImage(playerimg, 340, 240, 50, 50);
     }
     playerimg.src = "playersrc.png";
     window.onload = render();
     render();