tslint / codelyzer / ng lint error: “for (… in …) statements must be filtered with an if statement”

Question

Lint error message:

src/app/detail/edit/edit.component.ts[111, 5]: for (... in ...) statements must be filtered with an if statement

Answer 1

A neater way of applying @Helzgate's reply is possibly to replace your 'for .. in' with

for (const field of Object.keys(this.formErrors)) {