JS TypeScript的Map对象及联合类型实战

let myMap = new Map();

let myMap = new Map([
        ["key1", "value1"],
        ["key2", "value2"]
    ]); 

let nameSiteMapping = new Map();

nameSiteMapping.set("Google", 1);
nameSiteMapping.set("Runoob", 2);
nameSiteMapping.set("Taobao", 3);

console.log(nameSiteMapping.get("Runoob"));

console.log(nameSiteMapping.has("Taobao"));   
console.log(nameSiteMapping.has("Zhihu"));  

console.log(nameSiteMapping.size);

console.log(nameSiteMapping.delete("Runoob"));  
console.log(nameSiteMapping);

nameSiteMapping.clear();           
console.log(nameSiteMapping);

tsc --target es6 test.ts

let nameSiteMapping = new Map();
 
nameSiteMapping.set("Google", 1);
nameSiteMapping.set("Runoob", 2);
nameSiteMapping.set("Taobao", 3);

for (let key of nameSiteMapping.keys()) {
    console.log(key);                  
}

for (let value of nameSiteMapping.values()) {
    console.log(value);                 
}

for (let entry of nameSiteMapping.entries()) {
    console.log(entry[0], entry[1]);   
}

for (let [key, value] of nameSiteMapping) {
    console.log(key, value);            
}

var val:string|number 
val = 12 
console.log("数字为 "+ val) 
val = "Runoob" 
console.log("字符串为 " + val)

var val;
val = 12;
console.log("数字为 " + val);
val = "Runoob";
console.log("字符串为 " + val);

function disp(name:string|string[]) { 
        if(typeof name == "string") { 
                console.log(name) 
        } else { 
                var i; 
                for(i = 0;i<name.length;i++) { 
                console.log(name[i])
                } 
        } 
} 
disp("Runoob") 
console.log("输出数组....") 
disp(["Runoob","Google","Taobao","Facebook"])

function sayRes(res: number | string) {
    if (res.length > 0) { // Error: 类型“number”上不存在属性“length”。
    }
}