html5 canvas redraw on resize

Question

I have two canvas elements and need them to be resized on buttons click.

<div class="sDetails"><div>
                        <div id="canvasDiv" style="width: 310px;"><canvas id="canvasGraph"></canvas></div></div>
<div class="kDetails"><div><div>
<div id="canvasDiv" style="width: 310px; height: 240px;"><canvas id="canvasGraph"></canvas></div></div>

and the script:

   var sketch;var sketch_sl;var onPaint;var canvas=null;var ctx=null;var tmp_ctx=null;
    function drawCanvas(div) {
        canvas = document.querySelector(div + " #canvasGraph");
        ctx = canvas.getContext('2d');
        sketch = document.querySelector(div + " #canvasDiv");
        sketch_sl = getComputedStyle(sketch);
        canvas.width = parseInt(sketch_style.getPropertyValue('width'));
        canvas.height = parseInt(sketch_style.getPropertyValue('height'));
        tmp_canvas = document.createElement('canvas');
        tmp_ctx = tmp_canvas.getContext('2d');
        tmp_canvas.id = 'tmp_canvas';
        tmp_canvas.width = canvas.width;
        tmp_canvas.height = canvas.height;
        sketch.appendChild(tmp_canvas);

the redraw function:

// here I must redraw my lines resized 2 times ( *cScale ) where cScale=2 or =1
function drawScales(ctx, canvas) 
        ctx.strokeStyle = 'green';
        ctx.fillStyle = 'green';
        ctx.beginPath();
        ctx.moveTo(5, 0);
        ctx.lineTo(0, canvas.height);
        scaleStep = 24*cScale;

for some reason it works really bad, old positions stay. Is there a way to completely delete the whole canvas and append it or redraw it completely?

I tried canvas.width=canvas.width, tried ctx.clearRect(0, 0, canvas.width, canvas.height);tmp_ctx.clearRect(0, 0, canvas.width, canvas.height);, tried $(".sDetails #canvasGraph")[0].reset();

logically, drawCanvas(".sDetails");drawLines(ctx, canvas); should redraw it from scratch but it will not.