Execute a collection of tasks together at a later time.

Batch.js

/**
 * Execute a collection of tasks together at a later time.
 *
 * This is occasionally useful when animating a lot of primitives on a Canvas
 * since batching certain operations that change the canvas state can
 * significantly improve drawing time (especially in older browsers).
 */
function Batch(before, after) {
  var tasks = [];
  this.addTask = function(task) {
    tasks.push(task);
  };
  this.clearTasks = function() {
    tasks = [];
  };
  this.execute = function() {
    var state = {task: -1, tasks: tasks.length};
    before(state);
    for (state.task++; state.task < state.tasks; state.task++) {
      tasks[state.task](state);
    }
    after(state);
  };
}