What could be causing the error I'm encountering when attempting to declare a local variable?

Question

What could be causing the error I'm encountering when attempting to declare a local variable?

I am new to TypeScript and am encountering an issue with variable declaration in my component function. I am trying to declare a local variable "contains" like this:

  setUpgrade($event) {
    
     contains : Boolean = this.selectedUpgrades.includes($event);

    //some logic
    
    }

However, I am getting an error on this line:

 contains : Boolean = this.selectedUpgrades.includes($event);

The error I am receiving is:

  Type 'boolean' is not assignable to type 'BooleanConstructor'.

Can someone help me understand why this error is happening during variable declaration?

angular typescript

Answer 1

Answer №1

The Boolean type is the result of calling the Boolean constructor:

const somethingStrange = new Boolean(Math.random() < 0.5);

This is generally not recommended as it can have unexpected behaviors. For instance, a Boolean object with false is considered truthy. Its typeof is also object, not boolean. It is better to use the boolean type instead.

const contains : boolean = this.selectedUpgrades.includes($event);

Alternatively, you can omit the type annotation and let TypeScript infer it automatically:

const contains = this.selectedUpgrades.includes($event);

This is often preferred as it reduces unnecessary code and makes the code easier to understand.

Answer 2

The Boolean type is the result of calling the Boolean constructor:

const somethingStrange = new Boolean(Math.random() < 0.5);

This is generally not recommended as it can have unexpected behaviors. For instance, a Boolean object with false is considered truthy. Its typeof is also object, not boolean. It is better to use the boolean type instead.

const contains : boolean = this.selectedUpgrades.includes($event);

Alternatively, you can omit the type annotation and let TypeScript infer it automatically:

const contains = this.selectedUpgrades.includes($event);

This is often preferred as it reduces unnecessary code and makes the code easier to understand.

What could be causing the error I'm encountering when attempting to declare a local variable?

Answer №1

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