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