How to draw a triangle border

Triangle is composed of three lines, but we need only ctx.lineTo () twice, because, ctx.closePath () will be connected together to the starting point of the path is as follows: 

function Draw () {
     var Canvas = document.getElementById ( 'canv' );
     IF (canvas.getContext!) return ;
     var CTX = canvas.getContext ( "2D" );
     // open path drawing 
    ctx.beginPath ();
     / / determining a path starting point 
    ctx.moveTo (30, 30 );
     // draw a path 
    ctx.lineTo (280, 280 );
     // draw a path 
    ctx.lineTo (280, 30 );
     // end path drawn with ctx.beginPath ( ) connected 
    ctx.closePath ();
     // stroke, or "presentation" 
    ctx.stroke () 
} 
Draw ();