Creating a TypeScript type declaration for a loop

Is there a more sophisticated method to cast day as the correct type, rather than using (<{P: string}>day).P without resorting to the generic any type when dealing with a day object obtained from underscore.js through the findWhere command?

Simply writing let period of day.P triggers this error:

TS2339:Property 'P' does not exist on type '{}'.

let day = _.findWhere(this.availabilityDays, {D: moment($scope.model.BookDate).format('YYYY-MM-DD')});
this.$scope.BookingPeriods.splice(0);
for (let period of (<{P: string}>day).P) {
    this.$scope.BookingPeriods.push(period);
}
typescript

Answer №1

Utilize an interface for better code structure

interface TimeFrame {
  time: string;
}

// within the class
public availableTimeFrames: TimeFrame[];

If the issue lies within the usage of _.findWhere, and it potentially returns a result as an object (not confirmed), then you can typecast the result using as keyword

let timeframe: TimeFrame = _.findWhere(this.availableTimeFrames, condition) as TimeFrame;

Answer №2

It appears that your focus for this task is solely on the "P" member. My suggestion would be to iterate over the day array and conduct the conversion beforehand, prior to initiating the for loop. This approach enhances readability and maintains a clear separation between your Moment entity and the working data.

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