var optionsStack = [ 'option1', undefined, 'option2', undefined, 'option3' ]; var optionsWereSet = false; var options, error; registerPlugin({ install: function(less, pluginManager, functions) { if (!optionsWereSet) { error = 'setOptions() not called before install'; } }, use: function() { var pos = optionsStack.indexOf(options); if (pos === -1) { error = 'setOptions() not setting option "' + opt + '" correctly'; } if (error) { throw new Error(error); } }, setOptions: function(opts) { optionsWereSet = true; options = opts; } });