title: Immutable update function is not working
body: <p>I am using immutable.js function update() and updateIn(). But the result is not getting as expected.</p>
  
  <pre><code>const initialState = Immutable.fromJS({cartList: [
          {
              id: 1,
              name: "Product One",
              quantity:1
          },{
              id: 2,
              name: "Product Two",
              quantity:2
          }],
      productList:[{
              name: "Product One",
              id: 1,
              availability:2
          },{
              name: "Product Two",
              id: 2,
              availability:2
          },{
              name: "Product Three",
              id: 3,
              availability:4
          }]});
  var action = {
              id: 2,
              name: "Product Two",
              quantity:2
          };
  
   initialState = initialState.updateIn(['cartList'], cartList =&gt; cartList.push(action)).toJS();
   initialState = initialState.updateIn(['productList'], productList =&gt; {
              productList.map(product =&gt; {
                      if(action.id ==  product.get("id")){
                          return product.update("availability", value =&gt; value-1);
                  } else
                          return product
              });
  }).toJS();
  
  console.log(initialState.toJS());
  </code></pre>
  
  <p>I tried it in jsfiddle. But there is no change in initialState.</p>
  
  <p>Thanks in Advance.</p>