gistfile1.txt

const defaultState = {
  "label": "default label",
  "icon": "./default.png",
}

const differentState = {
  "label": "different label",
  "icon": "./different.png",
}

var { ActionButton } = require("sdk/ui/button/action");

var button = ActionButton({
    id: "default-label",
    label: "default label",
    icon: "./default.png",
    onClick: function(state) {
      if (button.label == "default label") {
        button.state(button, differentState);
      }
      else {
        button.state(button, defaultState);
      }
      console.log(button.state(button).label);
      console.log(button.state(button).icon);
    }
  });