Creating My First Type Definition

Typescript Main Point

One of reasons the typescript was invented is to get javascript errors to be detected in compilation step.
For example:
If you defined function myFunc and it suppose to be called without any params, and your code use its call in multipple places:

function myFunc() {
  alert('my name is Shlomo');
}
//call
myFunc()

And after some time you decided to change function code to use the parameter:

function myFunc(nm) {
  alert('my name is ' + nm);
}
//call
myFunc('Shlomo')

In case you using javascript and you forgot to change call in some place to its new shape - you will got 'nm is undefined' error when code will try to run following call.

//call
myFunc()

in typescript After you changed myFunc definition to use parameter:

myFunc(nm:string) {
  alert('my name is ' + nm);
}
//call
myFunc()//this will not compile

If there are some calls which not using parameter left- Typescript compiler will fail.

What are type definitions?

So if you use typescript and want to use some javascript library or plugin in your code - this plugin and its methods need to be defined in a way that typescript will "recognize" it.

Experiment With Selectize

For example purposes lets take our old angular-seed project which uses typescript. To demonstrate what happen when you try to use some javascript plugin inside typescript project lets install selectize.js jquery plugin

bower install selectize --save-dev

And place the call to the plugin inside View2Ctrl controller:

As you can see - trying to use the plugin as it is made vscode angry
You can see also compilation error:

Create Starter Definition File

As we can see in other definitions - the selective definition must be hosted inside node_modules/@types directory. lets add selectize directory and add index.d.ts file inside it. I will not write here about create real definition - since guys much wiser than me already created it here,
My purpose now is only to create something that make the typescript compiler calm.

/// <reference types="jquery"/>

declare namespace Selectize {
 
}
interface JQuery {
    selectize(options?: any): JQuery;
}

As you can see - i only added selectize method to Jquery interface
That is enough for get the source compiled -

Thanks For reading