typescript学习-基础类型

Posted 2020-10-13

/**
 * 布尔值
 */
let isDone: boolean = false;

/**
 * 数字
*/
let decLiteral: number = 6;
let hexLiteral: number = 0xf00d;

/**
 * 字符串
*/
let userName: string = `smith`;

/**
 * 数组
*/
let list: number[] = [1, 2, 3];
let list2: Array<number> = [1, 2, 3];

/**
 * 元组
*/
let x: [string, number];
x = [‘hello‘, 10];
x[2] = ‘world‘;
// console.log(x);

/**
 * 枚举
*/
enum Color { Red = 1, Green, Blue };
let colorName: string = Color[1];
// console.log(colorName);

/**
 * Any
*/
let notSure: any = 4;
notSure = ‘maybe a string instead‘;
notSure = false;
// console.log(notSure);
// notSure.ifItExists();
// notSure.toFixed();

let lists: any[] = [1, true, ‘free‘];
lists[1] = 100;
// console.log(lists);

/**
 * Void
*/
function warnUser(): void {
    alert(‘This is my warning message‘);
}
// warnUser();
let unusable: void = undefined;
let unusable2: void = null;


/**
 * Never
*/

function error (message:string):never{
    throw new Error(message);
}

function fail(){
    return error(‘something failed‘);
}

function infiniteLoop():never{
    while(true){
    }
}
// console.log(fail())

/**
 * 类型断言
*/ 

let someValue:any=‘this is a string‘;

let strLength:number=(<string>someValue).length;
let strLength2:number=(someValue as string).length;