javascript - clearRect function doesn't clear the canvas

Question

I'm using this script on the body onmousemove function:

function lineDraw() {
    // Get the context and the canvas:
    var canvas = document.getElementById("myCanvas");
    var context = canvas.getContext("2d");
    // Clear the last canvas
    context.clearRect(0, 0, canvas.width, canvas.height);
    // Draw the line:
    context.moveTo(0, 0);
    context.lineTo(event.clientX, event.clientY);
    context.stroke();
}

It's supposed to clear the canvas each time I move the mouse around, and draw a new line, but it isn't working properly. I'm trying to solve it without using jQuery, mouse listeners or similar.

Here is a demo: https://jsfiddle.net/0y4wf31k/

question from:https://stackoverflow.com/questions/13435959/clearrect-function-doesnt-clear-the-canvas

Answer 1

You should use "beginPath()". That is it.

function lineDraw() {   
    var canvas=document.getElementById("myCanvas");
    var context=canvas.getContext("2d");
    context.clearRect(0, 0, context.width,context.height);
    context.beginPath();//ADD THIS LINE!<<<<<<<<<<<<<
    context.moveTo(0,0);
    context.lineTo(event.clientX,event.clientY);
    context.stroke();
}