[TS] type alias

Basic usage

• type： Type aliases are used to give a type a new name , You can use the same type multiple times and use the same name .

• type Type alias syntax ：

type Point = {
    
  x: number;
  y: number;
};
 
function printCoord(pt: Point) {
    
  console.log("The coordinate's x value is " + pt.x);
  console.log("The coordinate's y value is " + pt.y);
}
 
printCoord({
     x: 100, y: 100 });

• You can use a type alias to name any type , Not just object types .
• Commonly used for union types .

type test = number; // Basic types 
let num: test = 10;
type userOjb = {
    name:string} //  object 
type getName = ()=>string  //  function 
type data = [number,string] //  Tuples 
type numOrFun = number | getName  //  Joint type