provide stack traces for browsers which don't have captureStackTrace

Author: defunctzombie

assert.js

@@ -58,6 +58,25 @@ assert.AssertionError = function AssertionError(options) {
   if (Error.captureStackTrace) {
     Error.captureStackTrace(this, stackStartFunction);
   }
+  else {
+    // non v8 browsers so we can have a stacktrace
+    var err = new Error();
+    if (err.stack) {
+      var out = err.stack;
+
+      // try to strip useless frames
+      var fn_name = stackStartFunction.name;
+      var idx = out.indexOf('\n' + fn_name);
+      if (idx >= 0) {
+        // once we have located the function frame
+        // we need to strip out everything before it (and its line)
+        var next_line = out.indexOf('\n', idx + 1);
+        out = out.substring(next_line + 1);
+      }
+
+      this.stack = out;
+    }
+  }
 };
 
 // assert.AssertionError instanceof Error