You may pass some options to the compiler:
var less = require('less');
less.render('.class { width: (1 + 1) }',
{
paths: ['.', './lib'], // Specify search paths for @import directives
filename: 'style.less', // Specify a filename, for better error messages
compress: true // Minify CSS output
},
function (e, output) {
console.log(output.css);
});
See for more information.