Saturday, February 8, 2014

Knockout Js Quick Start



Knockout js is a Javascript library which follows MVVM. It interacts or binds model with dom(view) element using ViewModel.  Now through this we can bind text, events, conditions and iterators(loop). The syntax is- data-bind=”<kind of binding> :<scope param>.  

 Example-
   <span data-bind="text: name"></span>

Another example-
   <div data-bind="if: address!=''"><span data-bind="text: address"></span></div>

Here, a conditional data binding is happening and under it, another text binding shown.

Now, let have a bit more in to it. It will cover few real scenarios-

HTML
   <div id="div_test">
    <ul data-bind="foreach: products"><!--scope starts-->
        <li><label data-bind="text: $index" ></label>&nbsp; <!--shows index count-->
            <span data-bind="text: name"></span>&nbsp;<!--conditional binding template starts-->
            <div data-bind="ifnot: rate > 20"><span data-bind="text: rate"></span></div>
            <div data-bind="with:plot">
                <span data-bind="text: width + '-' +height"></span></div> 
            <a data-bind="attr: {href:'#/'+name}" >click</a>          
            <div data-bind="if: address!=''"><span data-bind="text: address"></span></div>
        </li>

<!--conditional binding template starts-->
     </ul>
<!--scope ends-->
     <button data-bind="click: onclick">Click</button><!--event binding-->
   </div>


 Javascript

function scope(){
    var $scope=this;

//Json binding---->
    $scope.products=[{name:"test",

                                   address:"agarpara",
                                   rate:22,
                                   plot:{width:1110,height:800}
                                 },               
                                {name:"test2",
                                  rate:18,
                                  plot:{width:1500,height:600}}];
//Event binding------>
    $scope.onclick=function(){
        alert("Clicked");
    };
}
ko.applyBindings(new scope(),document.getElementById("div_test"));//apply a scope by a dom id


Few more working examples are in here
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