less.js/test/browser/runner-main-options.js

var less = {
    logLevel: 4,
    errorReporting: "console"
};
less.functions = {
    add: function(a, b) {
        return new(less.tree.Dimension)(a.value + b.value);
    },
    increment: function(a) {
        return new(less.tree.Dimension)(a.value + 1);
    },
    _color: function(str) {
        if (str.value === "evil red") {
            return new(less.tree.Color)("600");
        }
    }
};