Mastering TypeScript 3 - Third Edition

Using type casting

We can, however, use the TypeScript language feature of type casting to help with writing ExtJS code. If we know what type of ExtJS object we are trying to create, we can cast the JavaScript object to this type, and then use TypeScript to check whether the properties we are using are correct for that type of ExtJS object. To help with this concept, let's just take the outer definition of the Ext.application into account. Stripped of the inner code, the call to the application function on the Ext global object would be reduced to this:

Ext.application( 
    { 
        // properties of an Ext.application 
        // are set within this JavaScript 
        // object block 
    } 
); 

Using the TypeScript declaration files, type casting, and a healthy dose of ExtJS ...