PUBLIC

The bridge between W3C, WHATWG and ECMAScript

JavaScript is the programming language of the web and is quickly gaining traction outside of the browser. PUBLIC.com is a testing ground and reference for all JavaScript APIs. Each reference page contains detailed descriptions and interactive examples like the following so you can quickly learn by doing.

Example:

<!-- Interactive examples running in your browser -->
<canvas id='canvas'></canvas>
<script>
  console.log('See console.log output here');

  var strings = ['Your html displays here',
                 'Simple API descriptions',
                 'Interactive examples',
                 'Learn by doing',
                 'Edit me now!',
                 ''];

  var canvas = document.getElementById('canvas');
  var context = canvas.getContext('2d');

  var fontHeight = 16;

  // Center of the text (vertically)
  var centerY = fontHeight / 2;
  context.textBaseline = 'middle';

  // Set the font properties
  context.font = fontHeight + 'px sans-serif';

  // Linear Interpolation
  var lerp = function(from, to, t) {
    return (to - from) * t + from;
  };

  // Create a simple list of keyframe
  var keyframes = [
    // Slide the text down
    { time: 500, /* ms */
      applyKeyframe: function(context, t) {
        // Animate the opacity and position
        context.globalAlpha = t;
        context.translate(0, lerp(-(centerY + fontHeight), 0, Math.sin(t * Math.PI / 2)));
      }
    },
    
    // Delay
    { time: 1500 }, /* ms */

    // Slide the text down
    { time: 350, /* ms */
      applyKeyframe: function(context, t) {
        context.globalAlpha = (1 - t);
        context.translate(0, lerp(0, centerY + fontHeight, Math.sin(t * Math.PI / 2)));
      }
    },

    // Stay hidden
    { time: 350, /* ms */
      applyKeyframe: function(context, t) {
        context.globalAlpha = 0;
      }
    },
  ];

  // Get the total length of the animation
  var totalTime = keyframes.reduce(function(t, keyframe) {
    return t + keyframe.time;
  }, 0);

  // Create a function that draws one frame of the animation
  var drawFrame = function(time) {
    context.clearRect(0, 0, canvas.width, canvas.height);

    var string = strings[((time / totalTime) | 0) % strings.length];

    time = time % totalTime;

    var keyframe;
    for (var i = 0; i < keyframes.length; i++) {
      keyframe = keyframes[i];
      if (time < keyframe.time) {
        break;
      }
      time -= keyframe.time
    }

    // Save the context's state (transforms, colors, etc)
    context.save();

    if (keyframe.applyKeyframe) {
      keyframe.applyKeyframe(context, time / keyframe.time);
    }

    context.fillText(string, 0, centerY);

    // Restore the state
    context.restore();

    // Register our callback for the next frame
    requestAnimationFrame(drawFrame);
  };

  requestAnimationFrame(drawFrame);
</script>

Run

Results:

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