Node.js Stream - Buffer to String gives [object Object]

I would like to be able to filter the output. However, I have a problem converting from buffer to string. console.log(JSON.stringify(obj.toString()));

keeps giving me [object Object]

which i can't use. How do I convert the buffer to a string so that I can filter the content to stdout?

//inject 'bower and javascript' files or just 'javascript' files
function injectStream(sourceStream, filesStream) {
    sourceStream
        .pipe(injector(filesStream, { ignorePath: 'app', addRootSlash: false }))
        .pipe(gulp.dest(INDEX_PATH_PARENT))
        .pipe(through2.obj(function(obj, enc, next) {
            console.log(JSON.stringify(obj.toString()));
            this.push(obj.contents);
            next();
    })).pipe(process.stdout)
}