var postProcessor = function() {}; postProcessor.prototype = { process: function (css) { return 'hr {height:50px;}\n' + css; } }; var postProcessorPlugin = { install: function(less, pluginManager) { pluginManager.addPostProcessor( new postProcessor()); } }; var less = {logLevel: 4, errorReporting: "console", plugins: [postProcessorPlugin]};