javascript - canvas how to move rect using arrows -

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i started learning canvas today, started off creating simple rectangle, need make rectangle move using arrow keys, moveto function doesn't seem anything, how can achieve this. code far

<html>     <head>         <title></title>     </head>      <body>         <canvas id="mycanvas" width="600" height="250" style="border:1px         solid black;">         </canvas>       <script type="text/javascript">         var canvas = document.getelementbyid("mycanvas");         var context = canvas.getcontext("2d");         context.fillstyle = "green";          var x = 50,y=5,w=100,h=100;         context.fillrect(x,y,w,h);          document.onkeydown = function move()         {             switch(window.event.keycode)             {                 case 37:                 {                     //left                     context.moveto(x++,y);                     break;                 }                 case 38:                 {                     console.log('up');                     break;                 }                 case 39:                 {                     console.log('right');                     break;                 }                 case 40:                 {                     console.log('down');                     break;                 }             }         }      </script>     </body>     </html>

you can't move rectangles around canvas after you've drawn them fillrect.

the canvas image, rectangle becomes unmovable shape painted on canvas.

to "move" shapes, must clear canvas , redraw shape in new position.

btw, context.moveto path command tells context move drawing pen specified location. not move existing shape on canvas.

for example, in keyhandler when responding left-arrow key:

  • change x coordinate leftward: x--;

  • clear canvas: context.clearrect(0,0,canvas.width,canvas.height);

  • redraw rectangle @ new position: context.fillrect(x,y,w,h);


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