If you specify -o <target>.html when running the emcc command, Emscripten generates an HTML file and automatically adds code to load the module to the end of the file. Here's what the loading code in the HTML file looks like with the contents of each Module function excluded:

var statusElement = document.getElementById('status');
var progressElement = document.getElementById('progress');
var spinnerElement = document.getElementById('spinner');

var Module = {
  preRun: [],
  postRun: [],
  print: (function() {...})(),
  printErr: function(text) {...},
  canvas: (function() {...})(),
  setStatus: function(text) {...},
  totalDependencies: 0,
  monitorRunDependencies: function(left) {...}
};

Module.setStatus('Downloading...');

window.onerror = function(event) {
  Module.setStatus('Exception thrown, see JavaScript console');
  spinnerElement.style.display = 'none';
  Module.setStatus = function(text) {
    if (text) Module.printErr('[post-exception status] ' + text);
  };
};

The functions within the Module object are present to detect and address errors, monitor the loading status of the Module, and optionally execute some functions before or after the run() method from the corresponding glue code file executes. The canvas function, shown in the following snippet, returns the <canvas> element from the DOM that was specified in the HTML file before the loading code:

canvas: (function() {
  var canvas = document.getElementById('canvas');
  canvas.addEventListener(
    'webglcontextlost',
    function(e) {
      alert('WebGL context lost. You will need to reload the page.');
      e.preventDefault();
    },
    false
  );

  return canvas;
})(),

This code is convenient for detecting errors and ensuring the Module is loaded, but for our purposes, we won't need to be as verbose.