10.typescript筆記_泛型函數和泛型接口 泛型類與泛型約束

1.泛型函數和泛型接口

function log<T>(value : T) : T{
    console.log(value);
    return value;
}

log<number>(1);
log<string>("1");
log<object>({});
log<string[]>(["1"])

interface Log<T> {
    (value : T) : T;
}
let myLog : Log<string>= log;
myLog("string");

let myLog1 : Log<number> = log;
myLog1(1);

let myLog2 : Log<Array<string>> = log;
myLog2(["1"]);

2.泛型類與泛型約束
注意泛型不能約束靜態成員

class Log1<T> {
    run (value : T) {
        console.log(value);
        return value;
    }
}

let log1 = new Log1<number>();
log1.run(1);

3.當泛型不傳時,可以是任意類型

let log2 = new Log1();
log2.run(1);
log2.run("1");
log2.run({});

4.泛型繼承接口,實現只能傳保護length的值

interface Length {
    length : number
}
function Log4<T extends Length> ( value : T) : T{
    console.log(value.length)
    return value;
}
Log4({length : 1});
Log4("1");
Log4([1,2,3]);