Javascript Self Invoked Functions

Question

Hi guys can you explain me the differences between this two kind of implementations?

 var vettoreC: Array<number> = [];
 vettoreC = vettoreA;
 this.moda = (function mode(vettoreC) {
 return vettoreC.sort((a, b) =>
 vettoreC.filter(v => v === a).length - vettoreC.filter(v => v === b).length
 ).pop();
 })();

and

var vettoreC: Array<number> = [];
 vettoreC = vettoreA;
 this.moda = this.calcolaModa (vettoreC);

where calcolaModa is

calcolaModa(vettore: Array<number>) {
 return vettore.sort((a, b) =>
 vettore.filter(v => v === a).length - vettore.filter(v => v === b).length
 ).pop();
 }

In the first case I have this error:

ERROR TypeError: Cannot read property 'sort' of undefined
 at mode (statistiche.component.ts:145)
 at statisticheComponent.webpackJsonp.128.statisticheComponent.calcolaStatistiche (statistiche.component.ts:148)
 at SafeSubscriber._next (statistiche.component.ts:72)
 at SafeSubscriber.__tryOrUnsub (Subscriber.js:238)
 at SafeSubscriber.next (Subscriber.js:185)
 at Subscriber._next (Subscriber.js:125)
 at Subscriber.next (Subscriber.js:89)
 at MapSubscriber._next (map.js:83)
 at MapSubscriber.Subscriber.next (Subscriber.js:89)
 at CatchSubscriber.Subscriber._next (Subscriber.js:125)

The second works correctly.

What could i do to make valid the first implementation?

Answer 1

With the first example, you'll need to pass the arguments in the last parentheses:

this.moda = (function mode(vettoreC) {
 return vettoreC.sort((a, b) =>
 vettoreC.filter(v => v === a).length - vettoreC.filter(v => v === b).length
 ).pop();
})(vettoreC);

Notice the last line where the vettoreC is mentioned again.

• Douwe de Haan: @MarcoNatale No problem, happy to help!