Implement _.isError

Author: jugglinmike

test/objects.js

@@ -437,6 +437,7 @@
       parent.iBoolean   = new Boolean(false);\
       parent.iUndefined = undefined;\
       parent.iObject     = {};\
+      parent.iError     = new Error();\
     </script>'
   );
   iDoc.close();
@@ -577,6 +578,20 @@
     ok(_.isUndefined(iUndefined), 'even from another frame');
   });
 
+  test('isError', function() {
+    ok(!_.isError(1), 'numbers are not Errors');
+    ok(!_.isError(null), 'null is not an Error');
+    ok(!_.isError(Error), 'functions are not Errors');
+    ok(_.isError(new Error()), 'Errors are Errors');
+    ok(_.isError(iError), 'even from another frame');
+    ok(_.isError(new EvalError()), 'EvalErrors are Errors');
+    ok(_.isError(new RangeError()), 'RangeErrors are Errors');
+    ok(_.isError(new ReferenceError()), 'ReferenceErrors are Errors');
+    ok(_.isError(new SyntaxError()), 'SyntaxErrors are Errors');
+    ok(_.isError(new TypeError()), 'TypeErrors are Errors');
+    ok(_.isError(new URIError()), 'URIErrors are Errors');
+  });
+
   if (window.ActiveXObject) {
     test('IE host objects', function() {
       var xml = new ActiveXObject('Msxml2.DOMDocument.3.0');

underscore.js

@@ -1029,8 +1029,8 @@
     return obj === Object(obj);
   };
 
-  // Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp.
-  _.each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp'], function(name) {
+  // Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp, isError.
+  _.each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp', 'Error'], function(name) {
     _['is' + name] = function(obj) {
       return toString.call(obj) == '[object ' + name + ']';
     };