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Canvas Clock Hands


Part IV - Draw Clock Hands

The clock needs hands. Create a JavaScript function to draw clock hands:

JavaScript:

function drawClock() {
  drawFace(ctx, radius);
  drawNumbers(ctx, radius);
  drawTime(ctx, radius);
}

function drawTime(ctx, radius) {
  const now = new Date();
  let hour = now.getHours();
  let minute = now.getMinutes();
  let second = now.getSeconds();
  //hour
  hour = hour%12;
  hour = (hour*Math.PI/6)+(minute*Math.PI/(6*60))+(second*Math.PI/(360*60));
  drawHand(ctx, hour, radius*0.5, radius*0.07);
  //minute
  minute = (minute*Math.PI/30)+(second*Math.PI/(30*60));
  drawHand(ctx, minute, radius*0.8, radius*0.07);
  // second
  second = (second*Math.PI/30);
  drawHand(ctx, second, radius*0.9, radius*0.02);
}

function drawHand(ctx, pos, length, width) {
  ctx.beginPath();
  ctx.lineWidth = width;
  ctx.lineCap = "round";
  ctx.moveTo(0,0);
  ctx.rotate(pos);
  ctx.lineTo(0, -length);
  ctx.stroke();
  ctx.rotate(-pos);
}
Try it Yourself »


Example Explained

Create a Date object to get hour, minute, second:

const now = new Date();
let hour = now.getHours();
let minute = now.getMinutes();
let second = now.getSeconds();

Calculate the angle of the hour hand, and draw it a length (50% of radius), and a width (7% of radius):

hour = hour%12;
hour = (hour*Math.PI/6)+(minute*Math.PI/(6*60))+(second*Math.PI/(360*60));
drawHand(ctx, hour, radius*0.5, radius*0.07);

Use the same technique for minutes and seconds.

The drawHand() routine does not need an explanation. It just draws a line with a given length and width.