test.js

var object = {
    method: function () {
       console.log('foo');         
    },
    
    method2: function () {
       var that = this;
       $('.button').on('click', function () {
            that.method();
       });
    }
}

var object = {
    method: function () {
       console.log('foo');         
    },
    
    method2: function () {
       $('.button').on('click', function () {
           object.method();
       });
    }
}