tnolet · January 15, 2018 21:00 · Mar 9, 2012
diff --git a/hook_method.js b/hook_method.js
@@ -0,0 +1,92 @@
+var install_hook_to = function(obj) {
+
+    if (obj.hook || obj.unhook) {
+        throw new Error('Object already has properties hook and/or unhook');
+    }
+
+    obj.hook = function(_meth_name, _fn, _is_async) {
+        var self = this,
+            meth_ref;
+
+        // Make sure method exists
+        if (! (Object.prototype.toString.call(self[_meth_name]) === '[object Function]')) {
+            throw new Error('Invalid method: ' + _meth_name);
+        }
+
+        // We should not hook a hook
+        if (self.unhook.methods[_meth_name]) {
+            throw new Error('Method already hooked: ' + _meth_name);
+        }
+
+        // Reference default method
+        meth_ref = (self.unhook.methods[_meth_name] = self[_meth_name]);
+
+        self[_meth_name] = function() {
+            var args = Array.prototype.slice.call(arguments);
+
+            // Our hook should take the same number of arguments 
+            // as the original method so we must fill with undefined
+            // optional args not provided in the call
+            while (args.length < meth_ref.length) {
+                args.push(undefined);
+            }
+
+            // Last argument is always original method call
+            args.push(function() {
+                var args = arguments;
+
+                if (_is_async) {
+                    process.nextTick(function() {
+                        meth_ref.apply(self, args);
+                    });
+                } else {
+                    meth_ref.apply(self, args);
+                }
+            });
+
+            _fn.apply(self, args);
+        };
+    };
+
+    obj.unhook = function(_meth_name) {
+        var self = this,
+            ref  = self.unhook.methods[_meth_name];
+
+        if (ref) {
+            self[_meth_name] = self.unhook.methods[_meth_name];
+            delete self.unhook.methods[_meth_name];
+        } else {
+            throw new Error('Method not hooked: ' + _meth_name);
+        }
+    };
+
+    obj.unhook.methods = {};
+};
+
+//// Example ////
+
+var stdout = process.stdout;
+
+install_hook_to(stdout);
+
+console.log('-- Sync');
+
+stdout.hook('write', function(string, encoding, fd, write) {
+    write('caught: ' + string);
+});
+
+console.log('foo');
+
+stdout.unhook('write');
+
+console.log('-- Async');
+
+stdout.hook('write', function(string, encoding, fd, write) {
+    write('caught async: ' + string);
+}, true);
+
+console.log('bar');
+
+stdout.unhook('write');
+
+console.log('baz');
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