Property 'filter' does not exist on type 'Object'

Question

After updating my code to HttpClient I can't get filter() to work with the response. I keep getting Property 'filter' does not exist on type 'Object':

TS :

liqOnChange(selection): void  {
        this.http.get(this.json_liq).subscribe(res => {
            this.arr = res.filter(
                res => res.id == selection.target.value);
        });
}

Answer 1

filter is an array method which cannot be used for objects in your case res .

First check if res is an array.

if(Array.isArray(res)){
   this.arr = res.filter(
                res => res.id == selection.target.value);
}

Or set type to res as (res: Array<any>)

If your api is returning an object, in most cases it should be, you can't use filter method here, you should be using it for an array inside res object.

Answer 2

Change this line:

this.http.get(this.json_liq).subscribe(res => {

to this:

this.http.get(this.json_liq).subscribe((res: any) => {

or better yet to this:

 this.http.get(this.json_liq).subscribe((res: Array<any>) => {

and you should be able to bypass your typechecking error at the compiler.

Here is some more info from the official docs :

The any type is a powerful way to work with existing JavaScript, allowing you to gradually opt-in and opt-out of type-checking during compilation. You might expect Object to play a similar role, as it does in other languages. But variables of type Object only allow you to assign any value to them - you can't call arbitrary methods on them, even ones that actually exist:

let notSure: any = 4;
notSure.ifItExists(); // okay, ifItExists might exist at runtime
notSure.toFixed(); // okay, toFixed exists (but the compiler doesn't check)

let prettySure: Object = 4;
prettySure.toFixed(); // Error: Property 'toFixed' doesn't exist on type 'Object'.

Answer 3

我认为您的资源不在数组中，请检查资源的类型，如果是数组，则过滤方法起作用。

Answer 4

Either the object is null or it is not an array
try to check if the object is not null and is an array with
if(res != null && Array.isArray(res))