node js check type of variable
if (typeof i != "number") {
console.log('This is not number');
}node js check type of variable
if (typeof i != "number") {
console.log('This is not number');
}custom types in typescript
// simple type
type Websites = 'www.google.com' | 'reddit.com';
let mySite: Websites = 'www.google.com' //pass
//or
let mySite: Website = 'www.yahoo.com' //error
// the above line will show error because Website type will only accept 2 strings either 'www.google.com' or 'reddit.com'.
// another example.
type Details = { id: number, name: string, age: number };
let student: Details = { id: 803, name: 'Max', age: 13 }; // pass
//or
let student: Details = { id: 803, name: 'Max', age: 13, address: 'Delhi' } // error
// the above line will show error because 'address' property is not assignable for Details type variables.
//or
let student: Details = { id: 803, name: 'Max', age: '13' }; // error
// the above line will show error because string value can't be assign to the age value, only numbers.check type of object typescript
function isFish(pet: Fish | Bird): pet is Fish {
return (<Fish>pet).swim !== undefined;
}
// Both calls to 'swim' and 'fly' are now okay.
if (isFish(pet)) {
pet.swim();
}
else {
pet.fly();
}typescript type of object values
const data = {
value: 123,
text: 'text'
};
type Data = typeof data["text"]; // StringCopyright © 2021 Codeinu
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