CodeMirror: Autocomplete demo

function getCompletions(token, context) {

  var found = [], start = token.string;

  function maybeAdd(str) {

    if (str.indexOf(start) == 0) found.push(str);

  }

  function gatherCompletions(obj) {

    if (typeof obj == "string") forEach(stringProps, maybeAdd);

    else if (obj instanceof Array) forEach(arrayProps, maybeAdd);

    else if (obj instanceof Function) forEach(funcProps, maybeAdd);

    for (var name in obj) maybeAdd(name);

  }

  if (context) {

    // If this is a property, see if it belongs to some object we can

    // find in the current environment.

    var obj = context.pop(), base;

    if (obj.className == "js-variable")

      base = window[obj.string];

    else if (obj.className == "js-string")

      base = "";

    else if (obj.className == "js-atom")

      base = 1;

    while (base != null && context.length)

      base = base[context.pop().string];

    if (base != null) gatherCompletions(base);

  }

  else {

    // If not, just look in the window object and any local scope

    // (reading into JS mode internals to get at the local variables)

    for (var v = token.state.localVars; v; v = v.next) maybeAdd(v.name);

    gatherCompletions(window);

    forEach(keywords, maybeAdd);

  }

  return found;

}