typescript generic function

1interface Lengthwise {
2    length: number;
3}
4
5function loggingIdentity<T extends Lengthwise>(arg: T): T {
6    console.log(arg.length);  // Now we know it has a .length property, so no more error
7    return arg;
8}
9

1class Person<T, U, C> {
2  name: T
3  age: U
4  hobby: C[]
5
6  constructor(name: T, age: U, hobby: C[]) {
7    this.name = name
8    this.age = age
9    this.hobby = hobby
10  }
11}
12
13const output = new Person<string, number, string>('john doe', 23, ['swimming', 'traveling', 'badminton'])
14console.log(output)

1function firstElement<Type>(arr: Type[]): Type {
2  return arr[0];
3}
4// s is of type 'string'
5const s = firstElement(["a", "b", "c"]);
6// n is of type 'number'
7const n = firstElement([1, 2, 3]);

1class GenericNumber<T> {
2    zeroValue: T;
3    add: (x: T, y: T) => T;
4}
5
6let myGenericNumber = new GenericNumber<number>();
7myGenericNumber.zeroValue = 0;
8myGenericNumber.add = function(x, y) { return x + y; };
9

1function identity<T>(arg: T): T {
2  return arg;
3}Try

1var x = 1;
2var y = 1;
3if (x == y) {
4  x = x + 1
5}