var preProcessor = function() {}; preProcessor.prototype = { process : function (src, extra) { var injected = '@color: red;\n'; var ignored = extra.imports.contentsIgnoredChars; var fileInfo = extra.fileInfo; ignored[fileInfo.filename] = ignored[fileInfo.filename] || 0; ignored[fileInfo.filename] += injected.length; return injected + src; } }; var preProcessorPlugin = { install: function(less, pluginManager) { pluginManager.addPreProcessor( new preProcessor()); } }; var less = {logLevel: 4, errorReporting: "console", plugins: [preProcessorPlugin]};