Added first shot at a development shell

src/d8.js

Index: src/d8.js
diff --git a/src/d8.js b/src/d8.js
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+// Copyright 2008 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// How crappy is it that I have to implement completely basic stuff
+// like this myself?  Answer: very.
+String.prototype.startsWith = function (str) {
+  if (str.length > this.length)
+    return false;
+  for (var i = 0; i < str.length; i++) {

[Kasper Lund, 2008/10/21 08:26:56]

How about using substring and string equality check?

+    if (str.charAt(i) != this.charAt(i))
+      return false;
+  }
+  return true;
+};
+
+function ToInspectableObject(obj) {
+  if (!obj && typeof obj === 'object') {
+    return undefined;

[Kasper Lund, 2008/10/21 08:26:56]

I don't trust undefined not to be overwritten by users. I would just use
'return' - or maybe 'return void 0'.

+  } else {
+    return Object(obj);
+  }
+}
+
+function GetCompletions(global, last, full) {
+  var full_tokens = full.split();
+  full = full_tokens.pop();
+  var parts = full.split('.');
+  parts.pop();
+  var current = global;
+  for (var i in parts) {

[Kasper Lund, 2008/10/21 08:26:56]

This looks weird. Do you really want all the keys (0, 1, ...) as strings? Why
not use a for (var i = 0; i < parts.length; i++)?

+    var part = parts[i];
+    var next = current[part];
+    if (!next)
+      return [];
+    current = next;
+  }
+  var result = [];
+  current = ToInspectableObject(current);
+  while (current !== undefined) {

[Kasper Lund, 2008/10/21 08:26:56]

I would use a typeof check against 'undefined' here. 

+    var mirror = new $debug.ObjectMirror(current);
+    var properties = mirror.properties();
+    for (var i in properties) {

[Kasper Lund, 2008/10/21 08:26:56]

Do you really want to use for-in here too?

+      var name = properties[i].name();
+      if (typeof name === 'string' && name.startsWith(last))
+        result.push(name);
+    }
+    current = ToInspectableObject(current.__proto__);
+  }
+  return result;
+}