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?

Douwe de Haan · Accepted Answer · 2017-05-31 09:04:11Z

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.

answered May 31, 2017 at 9:04

Douwe de Haan

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1 Comment

Douwe de Haan Over a year ago

@MarcoNatale No problem, happy to help!

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