A browser based same-game clone written in Javascript using SVG with Raphael.js
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README.md
eboc.js
eboc.view.svg.js
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raphael.2.2.1.min.js
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README.md

Exploding Boxes of Color (Eboc)

Eboc started as a quick weekend project back in 2012. I was considering using Raphael.js for a project, and figured building a game would be a good way to test the framework. I've refactored it since then.

The game is a color matching, falling block game that I broke up into a model and view. The model contains the column structures and adjacency data. The view asynchronously animates game state transitions. Some animations are purely cosmetic, and do not interupt the game state. The ones that do used chained promises to ensure that game states do not transition until the animation is complete.

Promises compose nicely, and work naturally whether the view chooses to kick off multiple aync animations serially, or in parallel.

How Eboc Uses Serial Promises

Eboc uses serial promises in a few places. For example, the end-of-level screen displays several lines of text, one after the other, then animates a counting score. The game model does not set up the next level until after the score has finished counting, or the user interrupts by clicking a "continue" button.

A helper method called _createLineExecutors() in Eboc.SvgView accepts lines of screen text as an array of strings. It returns an array of "executors", functions which can be passed to the Promise constructors that perform an asynchronous action, then either call resolve(), reject() or return another promise. A simplified version of the Eboc function looks like this:

  function _createLineExecutors(lineTexts) {
    const lineHeight = 10;
    return lineTexts.map((text, lineNumber)=>{
      return (resolve)=>{
        r.paper.text(0,lineY += lineHeight, text).animate({fontSize:20}, 500, resolve);
      };
    }
  }

Other executors can be appended to this array, and the final array chained together:

  function showEndLevel(score) {
    let executors = _createLineExecutors([`The Score is: ${score}`, "Well Done!", this._animateScoreCounting]);
    return = executors.reduce((chain, promise)=>{
      return chain.then(()=> {
        return new Promise(promise);
      });
    }, Promise.resolve());
  }

When showEndLevel() is called, it returns a promise. The model can then tell the view to show the ending lines, and only increment the model state after the view is done.

  async function endLevel() {
    await view.showEndLevel()
    this.currentLevel++;
    this.resetLevel();
  }

How Eboc Uses Parallel Promises

Eboc runs parallel promises using the all() method on an array of promises. For example, when animating all blocks dropping:

Eboc.SvgView.prototype.showBoxesDropping = async function(boxesToDrop) {
  return Promise.all(boxesToDrop.map(function(box){
    return new Promise((resolve)=> {
      let originalY = box.y;
      box.y = originalY + box.fallingBy;
      box.fallingBy = 0;
      box.view.animate({
        y: box.y
      }, 500, "bounce", resolve);
    });
  }));
}