TypeScript----函数

function add(x:number,y:number):number{
    return x+y;
}
 
let myAdd=function(x:number,y:number):number{
    return x+y;
}
 
let myAdd1:(x:number,y:number)=>number=function(x:number,y:number):number{
    return x+y;
}

二、函数参数形式

(1)可选参数，参数名旁使用 ? ，可选参数必须跟在必须参数后面 。

function buildName(firstName: string, lastName?: string) {
    if (lastName)
        return firstName + " " + lastName;
    else
        return firstName;
}
let result1 = buildName("Bob");  // works correctly now
let result2 = buildName("Bob", "Adams", "Sr.");  // error, too many parameters
let result3 = buildName("Bob", "Adams");  // ah, just right

(2) 默认参数，=，可以传入undefined值

function buildName1(firstName: string, lastName = "Smith") {
    return firstName + " " + lastName;
}
 
let result4 = buildName1("Bob");                  // works correctly now, returns "Bob Smith"
let result5 = buildName1("Bob", undefined);       // still works, also returns "Bob Smith"
let result6 = buildName1("Bob", "Adams", "Sr.");  // error, too many parameters
let result7 = buildName1("Bob", "Adams");         // ah, just right

(3)剩余参数

function buildName2(firstName: string, ...restOfName: string[]) {
    return firstName + " " + restOfName.join(" ");
}
 
let employeeName = buildName2("Joseph", "Samuel", "Lucas", "MacKinzie");

三、函数中的this，箭头函数

四、函数重载

参数不同，函数名相同