|
@@ -5,13 +5,13 @@ let a: 10;
|
|
|
let b: 'man' | 'woman';
|
|
let b: 'man' | 'woman';
|
|
|
b = 'man';
|
|
b = 'man';
|
|
|
b = 'woman'
|
|
b = 'woman'
|
|
|
-let c1: number = 10;
|
|
|
|
|
-let c2: string = '10';
|
|
|
|
|
-let c3: null = null;
|
|
|
|
|
-let c4: undefined = undefined;
|
|
|
|
|
-let c5: boolean = true;
|
|
|
|
|
-let c6: symbol = Symbol("xxx");
|
|
|
|
|
-let c7: bigint = BigInt(5637742873827823784);
|
|
|
|
|
|
|
+// let c1: number = 10;
|
|
|
|
|
+// let c2: string = '10';
|
|
|
|
|
+// let c3: null = null;
|
|
|
|
|
+// let c4: undefined = undefined;
|
|
|
|
|
+// let c5: boolean = true;
|
|
|
|
|
+// let c6: symbol = Symbol("xxx");
|
|
|
|
|
+// let c7: bigint = BigInt(5637742873827823784);
|
|
|
// null undefined区别
|
|
// null undefined区别
|
|
|
// b = 12;
|
|
// b = 12;
|
|
|
// 任意类型 隐性
|
|
// 任意类型 隐性
|
|
@@ -34,4 +34,35 @@ e = '12';
|
|
|
let f:string;
|
|
let f:string;
|
|
|
// f = d;
|
|
// f = d;
|
|
|
// f = e;
|
|
// f = e;
|
|
|
-export { }
|
|
|
|
|
|
|
+
|
|
|
|
|
+/**
|
|
|
|
|
+ * 类型断言
|
|
|
|
|
+ * 告知ts 开发者确定当前的值是什么目标类型 强制跳过了类型的判断
|
|
|
|
|
+ * 格式:
|
|
|
|
|
+ *
|
|
|
|
|
+ * f = d as string;
|
|
|
|
|
+ * f = <string>d;
|
|
|
|
|
+ * */
|
|
|
|
|
+f = d as string;
|
|
|
|
|
+f = <string>d;
|
|
|
|
|
+let val:any = 'hello';
|
|
|
|
|
+let str = val as string;
|
|
|
|
|
+// 类型转换
|
|
|
|
|
+let x = '123';
|
|
|
|
|
+let y = Number(x);
|
|
|
|
|
+
|
|
|
|
|
+// void 用于表示空 函数没有返回值
|
|
|
|
|
+// function fn1():void {
|
|
|
|
|
+// console.log("fn1");
|
|
|
|
|
+// // return 12;
|
|
|
|
|
+// }
|
|
|
|
|
+
|
|
|
|
|
+// never 永远不会有结果 函数永远执行不完
|
|
|
|
|
+function fn1():never {
|
|
|
|
|
+ throw new Error("报错")
|
|
|
|
|
+ // console.log("fn1");
|
|
|
|
|
+ // return 12;
|
|
|
|
|
+}
|
|
|
|
|
+console.log(fn1())
|
|
|
|
|
+// export { }
|
|
|
|
|
+
|