Angular 2 - Cannot read property of undefined error using Array.filter

Question

folks, I am working on a project that needs to filter JSON but in developer tools of Chrome, it shows me an error of undefined property.

 chart: JsonChart[] = [];
 charts: JsonCharts[] = [];

 getCharts() {
    this.iChartHttp.getCharts()
        .subscribe(
        charts => this.charts = charts, //return json object
        error => this.errorMessage = <any>error
        );
}

 if (this.chart_id != null) {
        this.getCharts();
         this.chart = this.charts.filter(charts => charts.id === this.chart_id)[0].series; // this like error occur.
    }

Updated Question

It's not getting JSON Array from Service. but it works in another component

iChartHttpService:

 getCharts(): Observable<JsonCharts[]> {
return this.http.get('assets/datas.json')
  .map((res: Response) => res.json())
  .do(data => console.log('server data:', data))  // debug
  .catch(this.handleError);
}

/**
* Handle HTTP error
*/
private handleError(error: any) {
// In a real world app, we might use a remote logging infrastructure
// We'd also dig deeper into the error to get a better message
const errMsg = (error.message) ? error.message :
  error.status ? `${error.status} - ${error.statusText}` : 'Server error';
console.error(errMsg); // log to console instead
return Observable.throw(errMsg);

}

Sajeetharan · Accepted Answer · 2017-06-04 13:32:00Z

2

It occurs when charts is null, try to place your filter logic after the results,

  getCharts() {
        this.iChartHttp.getCharts()
            .subscribe((charts: any) => {
            this.charts = charts, //return json object
            this.chart = this.charts.filter(charts => charts.id === this.chart_id)[0].series; 
            }, error => {
                error => this.errorMessage = <any>error
            });
    }

edited Jun 4, 2017 at 13:32

answered Jun 4, 2017 at 12:09

Sajeetharan

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10 Comments

Adnan Over a year ago

why charts getting null?

Adnan Over a year ago

@ Sajeetharan I didn't get that, the this.charts is declared in outside of getcharts() method so it may not be getting null after the subscribe

Adnan Over a year ago

@Sajeedtharan Yes but it gets error: Argument of type 'JsonChart[]' is not assignable to parameter of type '(error: any) => void'. Type 'JsonChart[]' provides no match for the signature '(error: any): void'.

Adnan Over a year ago

it seems it didn't pass any JSON object, but in service, it's getting JSON object from API

Adnan Over a year ago

not it's not :) but I see the method didn't return any JSON object from iChartHttp.getCharts(). But in iChartHttp.getCharts() it's logs JSON array successfully

|

Sachila Ranawaka · Accepted Answer · 2017-06-04 12:53:39Z

1

I think you need to send the series inside the javascript filter function. modify it like this

if (this.chart_id != null) {
    this.getCharts();
    if (this.chart.length > 0) {
        this.chart = this.charts.filter(charts => {
            if (charts.id === this.chart_id) {
                charts[0].series;
            }
        })
    }
}

answered Jun 4, 2017 at 12:53

Sachila Ranawaka

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1 Comment

Adnan Over a year ago

thank you sachila but the this.charts is getting null

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