Angular 4 - .filter is not a function

Question

I have this code:

 transform(searchData: Array<vw_WebSiteCourseSearch>, searchResultContentType: string) {
        if (searchData == undefined) {
            return;
        }

        return searchData.filter((item) => item.ContentType == searchResultContentType);
    }

My console prints:

ERROR TypeError: searchData.filter is not a function
at FilterCountPipe.webpackJsonp.../../../../../src/app/Common/pipes/filterCount.pipe.ts.FilterCountPipe.transform (filterCount.pipe.ts:19)

I tried to add import from rxjs/add/operator/filter, but it didn't solved it. Any ideas on how to fix it?

Thanks

Answer 1

Should searchData be null (or undefined), you should get an error like

TypeError: cannot read property filter of null  // or undefined

Like @OscarPaz thought, filter is not a function is thrown because the received searchData is not an array (yet still defined and not null).