Typescript array of key value pairs declaration

Yes, like you guessed, it’s a js object with key as string and AbstractControl as values.
For example:

{
    "control1": new Control(),
    "control2": new Control()
}

Edit

You can declare a variable to be of this type in two ways:

let controls: { [key: string]: AbstractControl };

or

interface ControlsMap {
    [key: string]: AbstractControl;
}

let controls: ControlsMap;

or even better:

interface ControlsMap<T extends AbstractControl> {
    [key: string]: T;
}

let controls1: ControlsMap<AbstractControl>;
let controls2: ControlsMap<MyControl>;