Edit in JSFiddle

(function(){
    var viewModel = function(options){
        var self = this;
        
        self.name = ko.observable(options.name);
    };
    
    vm = new viewModel({name:"knockout.js"});

    ko.applyBindings(vm);
})();

<input type="text" data-bind="value:name"/>
<p>
    Merhaba <span data-bind="text:name"/>
</p>