cnpm i typescript -g

tsc helloworld.ts

{
  "compilerOptions": {
    /* Visit https://aka.ms/tsconfig to read more about this file */
    /* Language and Environment */
    "target": "es2016",                                  
    /* Modules */
    "module": "commonjs",                                
    "esModuleInterop": true,                              
    "forceConsistentCasingInFileNames": true,            /* Ensure that casing is correct in imports. */
    /* Type Checking */
    "strict": true,                                      /* Enable all strict type-checking options. */
    "skipLibCheck": true                                 /* Skip type checking all .d.ts files. */
  }
}

// Basic DataStruct introduction
let married:boolean = true;
let age:number = 10;
let first_name:string = 'guoming';
let arr1:number[] = [1,2,3];
let arr2:Array<number> = [4,5,6]
// tuple, number and type are know to us
let guoming:[string,number] = ['guoming',10];
// enum type
enum Gender {
    GIRL,
    BOY
}
// basic enum
console.log(Gender.BOY)
console.log(Gender.GIRL)
// const enum
const enum Colors{
    RED,YELLOW,BLUE
}
let myColor = [Colors.RED,Colors.YELLOW,Colors.BLUE]
// any type,if there is an variable declared to be any,these variable is the same like the variable in JavaScript
let root:any = document.getElementById('root')
root.style.color = 'red'
let element: (HTMLElement|null) = document.getElementById('root');
element.style.color = 'green';
// null undefined
let x:number;
x=1;
x=undefined;
x=null;
let y:(number|null|undefined)
y=1;
y=null;
y=undefined;

let res =document.getElementById('test');  //HTMLElement
let el = document.querySelector('# test');  // Element