angular - Do I need constructor body in Angular2? -

i couldn't find difference between:

constructor (private router: router) { } 

and

router: router;      constructor (private _router: router) {        this.router = _router } 

variable router available in whole class , contains same data. what's difference between first , second syntax?

basically this:

constructor (private router: router) { } 

is short form of this:

private router: router;      constructor (_router: router) {     this.router = _router }   

personally use first format in projects because makes files shorter, , easier read.

if question block inside of constructor, answer - no. if using short form showed before, there no need put in constructor. needed init stuff can put in ngoninit function.

short example:

@component({   selector: 'my-cmp',   template: `<p>my-component</p>` }) class mycomponent implements oninit { constructor(     private router: router,     private myservice: myservice ) { }    ngoninit() {     console.log('ngoninit');   } }