Boolean is the data type that has two possible values. It is either true or false.
To do type checking on the variable we can write a statement as follows
const isTrue : boolean = true;
Step-by-step:
- Define variable
const isTrue
- Add typescript type check
: boolean
- Define value
true
To check whether function is returning boolean we can do it as fallows:
function isOlder(age : number) : boolean {
return age >= 18 ? true : false;
}
isOlder(18) // true
isOlder(16) // false
isOlder(true) // error 'Argument of type boolean is not assignable to parameter of type number'
Step-by-step:
- Define function
function isOlder(argument : typecheck) : type to return {...}
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