typescript generics code example

Example 1: extend generics in functions typescript

interface Lengthwise {
    length: number;
}

function loggingIdentity<T extends Lengthwise>(arg: T): T {
    console.log(arg.length);  // Now we know it has a .length property, so no more error
    return arg;
}

Example 2: typescript generic class

class Person<T, U, C> {
  name: T
  age: U
  hobby: C[]

  constructor(name: T, age: U, hobby: C[]) {
    this.name = name
    this.age = age
    this.hobby = hobby
  }
}

const output = new Person<string, number, string>('john doe', 23, ['swimming', 'traveling', 'badminton'])
console.log(output)

Example 3: typescript generic function

function firstElement<Type>(arr: Type[]): Type {
  return arr[0];
}
// s is of type 'string'
const s = firstElement(["a", "b", "c"]);
// n is of type 'number'
const n = firstElement([1, 2, 3]);

Example 4: typescript class type t

class GenericNumber<T> {
    zeroValue: T;
    add: (x: T, y: T) => T;
}

let myGenericNumber = new GenericNumber<number>();
myGenericNumber.zeroValue = 0;
myGenericNumber.add = function(x, y) { return x + y; };

Example 5: typescript generic type

function identity<T>(arg: T): T {
  return arg;
}Try

Example 6: how to make a generic variable in javascript

var x = 1;
var y = 1;
if (x == y) {
  x = x + 1
}