08: add my JavaScript code

skatsuta · skatsuta · commit 1bbfef75dbcc · 2016-12-11T16:35:01.000+09:00
Signed-off-by: Soshi Katsuta &lt;soshi.katsuta@gmail.com&gt;
diff --git a/08 - Fun with HTML5 Canvas/index-START.html b/08 - Fun with HTML5 Canvas/index-START.html
@@ -6,8 +6,7 @@
 </head>
 <body>
 <canvas id="draw" width="800" height="800"></canvas>
-<script>
-</script>
+<script src="index.js"></script>
 
 <style>
   html, body {
diff --git a/08 - Fun with HTML5 Canvas/index.js b/08 - Fun with HTML5 Canvas/index.js
@@ -0,0 +1,55 @@
+class Painter {
+  constructor(ctx) {
+    ctx.strokeStyle = '#BADA55';
+    ctx.lineJoin = 'round';
+    ctx.lineCap = 'round';
+    this.ctx = ctx;
+
+    this.MIN_LINE_WIDTH = 1;
+    this.MAX_LINE_WIDTH = 100;
+
+    this.isDrawing = false;
+    this.lastX = this.lastY = 0;
+    this.hue = 0;
+    this.direction = true;
+  }
+
+  draw(e) {
+    if (!this.isDrawing) { return; }
+
+    const ctx = this.ctx;
+    ctx.strokeStyle = `hsl(${this.hue}, 100%, 50%)`;
+    ctx.beginPath();
+    ctx.moveTo(this.lastX, this.lastY);
+    ctx.lineTo(e.offsetX, e.offsetY);
+    ctx.stroke();
+
+    [this.lastX, this.lastY] = [e.offsetX, e.offsetY];
+    this.hue < 360 ? this.hue++ : this.hue = 0;
+
+    if (ctx.lineWidth <= this.MIN_LINE_WIDTH || ctx.lineWidth >= this.MAX_LINE_WIDTH) {
+      this.direction = !this.direction;
+    }
+    this.direction ? ctx.lineWidth++ : ctx.lineWidth--;
+  }
+
+  startDrawing(e) {
+    this.isDrawing = true;
+    [this.lastX, this.lastY] = [e.offsetX, e.offsetY];
+  }
+
+  stopDrawing() {
+    this.isDrawing = false;
+  }
+}
+
+const canvas = document.querySelector('#draw');
+canvas.width = window.innerWidth;
+canvas.height = window.innerHeight;
+const painter = new Painter(canvas.getContext('2d'));
+[
+  { eventType: 'mousemove', callback: e => painter.draw(e) },
+  { eventType: 'mousedown', callback: e => painter.startDrawing(e) },
+  { eventType: 'mouseup',   callback: () => painter.stopDrawing() },
+  { eventType: 'mouseout',  callback: () => painter.stopDrawing() }
+].forEach(({eventType, callback}) => canvas.addEventListener(eventType, callback));
