Set default value of boolean typescript

Question

I have an object:

export class ReccurrenceModel {
    fromDate: Date;
    toDate: Date;
    weeklyReccurrence: number;
    state: State;
    isMonday: boolean;
    isTuesday: boolean;
    isWednesday: boolean;
    isThursday: boolean;
    isFriday: boolean;
    fromDateToReturn: Date;
    toDateToReturn: Date;
}

I use it like this

  if (this.reccurrenceSelected === true) {
      this.reccurrence.isMonday = this.mondaySelected;
      this.reccurrence.isTuesday = this.tuesdaySelected;
      this.reccurrence.isWednesday = this.wednesdaySelected;
      this.reccurrence.isThursday = this.thursdaySelected;
      this.reccurrence.isFriday = this.fridaySelected;
}

I want to set a default value for them - false because if I do not set them in in UI, they will be undefined and I don't want that.

How to set de default value of a boolean in typescript?

@FatemeFazli this gives a lint error for redundancy (just to inform) — , Nov 19 '18 at 11:27

Pardeep Jain · Accepted Answer · 2018-11-20T08:31:09.920

14

Doesn't make any big change in UI level you can use either. Both are falsy values for UI.

You can set anyone.

variableName = false

or

variableName: boolean;

variableName you can use either UI consider it as false by default untill you assign its value to true.

edited Nov 20 '18 at 08:31

answered Nov 19 '18 at 11:27

Pardeep Jain

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CruelEngine · Answer 2 · 2018-11-20T05:22:23.470

I would add a default constructor and do something like this :

export class ReccurrenceModel {
    fromDate: Date;
    toDate: Date;
    weeklyReccurrence: number;
    state: State;
    isMonday: boolean;
    isTuesday: boolean;
    isWednesday: boolean;
    isThursday: boolean;
    isFriday: boolean;
    fromDateToReturn: Date;
    toDateToReturn: Date;

    constructor(){
      this.isMonday = false;
      this.isTuesday = false;
      this.isWednesday = false;
      this.isThursday = false;
      this.isFriday = false;
    }
}

later i would do something like this : ,

this.reccurrence = new ReccurrenceModel();

The above line would initialize the required fields. you can confirm this by doing a console.log(this.reccurrence) after calling the constructor

score 5 · Answer 3 · answered Nov 19 '18 at 11:26

undefined, as well as false, are both falsy values that you can test the same way.

But default values are set with

export class ReccurrenceModel {
    fromDate: Date;
    toDate: Date;
    weeklyReccurrence: number;
    state: State;
    isMonday = false;
    isTuesday = false;
    ...
    fromDateToReturn: Date;
    toDateToReturn: Date;
}

Rohit.007 · Answer 4 · 2018-11-19T11:36:20.460

I would suggest to use getters and setters in class

export class ReccurrenceModel {
    fromDate: Date;
    toDate: Date;
    weeklyReccurrence: number;
    state: State;
    isMonday: boolean;
    isTuesday: boolean;
    isWednesday: boolean;
    isThursday: boolean;
    isFriday: boolean;
    fromDateToReturn: Date;
    toDateToReturn: Date;
        ...

        get fromDate() {
            return this.fromDate|| "";
        }
        get isMonday() {
            return this.isMonday|| false;
        }
    }

score 1 · Answer 5 · answered Oct 06 '19 at 16:27

You can put

      this.isMonday = false;
      this.isTuesday = false;
      this.isWednesday = false;
      this.isThursday = false;
      this.isFriday = false;

these in ngOnInit() method also, this is the method which is called first. to find the difference between ngOnInit() and constructor visit Difference between Constructor and ngOnInit

Set default value of boolean typescript

5 Answers5