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@@ -0,0 +1,68 @@
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+/**
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+ * 字面量
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+ * 1 2 3 4 5 true false
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+ *
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+ * 变量
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+ * var 变量名 = 变量值;
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+ *
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+ * 两种：
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+ * 基本数据类型：number boolean string null undefined symbol bigint
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+ * 引用数据类型: object (数组 对象 函数)
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+ *
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+ * ts 定义类型
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+ * let xx:type = value;
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+ */
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+
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+let a: string = '12';
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+let b: number = 121;
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+let c: boolean = false;
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+let d: null = null;
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+let e: undefined = undefined;
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+let f: symbol = Symbol('mySymbol');
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+let g: bigint = 647732672647264726n;
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+
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+
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+// ts专属类型
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+
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+// any 任意类型 隐性类型
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+let h;
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+h = 123;
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+h = 'str1';
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+
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+// unknown 未知类型 显性类型
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+let i: unknown;
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+i = 123;
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+i = 'str2';
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+
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+/** any unknown 区别
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+ * any 可以赋值给任意类型
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+ * unknown 只能赋值给 unknown 和 any
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+**/
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+let j: string;
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+// h = i;
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+// j = h;
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+
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+/**
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+ * 类型断言
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+ * 1.数据 as 类型
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+ * 2.<类型>数据
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+ */
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+
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+j = i as string;
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+j = <string>i;
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+
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+// void 空类型 函数没有返回值
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+function fn1():void {
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+ console.log('fn1');
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+ // return 12;
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+}
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+fn1();
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+
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+// never 永远不会有返回值
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+function fn2():never {
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+ // console.log('fn2');
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+ // return 12;
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+ throw new Error('报错了');
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+}
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+fn2();
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+
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zheng