TypeScript函数

1.函数类型

/*
js写法:
function add(x,y){//命名函数
return x+y;
}

var myAdd=function(x,y){//匿名函数
return x+y;
}*/
/*
ts写法*/
function add(x:number,y:number):string{//命名函数
//    return x+y;//返回number类型
return "mm";
}

var myAdd = function (x:number,y:string):string {//匿名函数
return "hi!";
};

/*name:string,age:number指定n和a的具体意义*/
var myAddts:(name:string,age:number) =>number = function (n:string,a:number):number {//==>后是返回值类型
return a;
};

/*
js写法:
function add(x,y){//命名函数
return x+y;
}

var myAdd=function(x,y){//匿名函数
return x+y;
}*/
/*
ts写法*/
function add(x, y) {
//    return x+y;//返回number类型
return "mm";
}
var myAdd = function (x, y) {
return "hi!";
};
/*name:string,age:number指定n和a的具体意义*/
var myAddts = function (n, a) {
return a;
};

2.可选和默认参数

/*可选参数  ?   */

function buildName(firstName:string,lastName:string){
return firstName + " " + lastName;
}

var result1 = buildName("ma","mz");
//var result2 = buildName("ma");//编译错误
//var result3 = buildName("ma","mz","");//编译错误

function buildName2(firstName:string,lastName?:string){
if(lastName){
return firstName + " " + lastName;
}else{
return firstName;
}
}

var result22 = buildName2("ma");//有?可有可无

/*
默认参数*/
function  buildName3(firstName:string,lastName="mm"){
return firstName+" "+lastName;
}
var r1=buildName3("m");//lastName是mm
var r2=buildName3("ma","mz");//lastName改为mz
//vae r3=buildName("ma","mz","");//编译错误

//document.getElementById("pid").innerHTML = r1;//m mm
document.getElementById("pid").innerHTML = r2;//ma mz

/*可选参数  ?   */
function buildName(firstName, lastName) {
return firstName + " " + lastName;
}
var result1 = buildName("ma", "mz");
//var result2 = buildName("ma");//编译错误
//var result3 = buildName("ma","mz","");//编译错误
function buildName2(firstName, lastName) {
if (lastName) {
return firstName + " " + lastName;
}
else {
return firstName;
}
}
var result22 = buildName2("ma"); //有?可有可无
/*
默认参数*/
function buildName3(firstName, lastName) {
if (lastName === void 0) { lastName = "mm"; }
return firstName + " " + lastName;
}
var r1 = buildName3("m"); //lastName是mm
var r2 = buildName3("ma", "mz"); //lastName改为mz
//vae r3=buildName("ma","mz","");//编译错误
//document.getElementById("pid").innerHTML = r1;//m mm
document.getElementById("pid").innerHTML = r2; //ma mz

3.可变参数

function peopleName(firstName:string,...restOfname:string[]){//...restOfname:string[]可变参数
return firstName+""+restOfname.join("-");
}

var pn = peopleName("m1","m2","m3","?");//可变参数,任意个
document.getE

function peopleName(firstName) {
var restOfname = [];
for (var _i = 1; _i < arguments.length; _i++) {
restOfname[_i - 1] = arguments[_i];
}
return firstName + "" + restOfname.join("-");
}
var pn = peopleName("m1", "m2", "m3", "?"); //可变参数,任意个
document.getElementById("pid").innerHTML = pn; //m1m2-m3-?

4.Lambads 和 this 关键字的使用

var people = {
name:["m1","m2","m3","m4"],
getName:function(){
/*return function () {
var i = Math.floor(Math.random()*4);
return{
n:this.name[i]//undefined this不是name数组

}
}*/

return ()=> {//Lambads 的使用
var i = Math.floor(Math.random()*4);
return{
n:this.name[i]//m*
}
}
}
};

var Myname = people.getName();
alert("名字:" +Myname().n);

var people = {
name: ["m1", "m2", "m3", "m4"],
getName: function () {
/*return function () {
var i = Math.floor(Math.random()*4);
return{
n:this.name[i]//undefined this不是name数组

}
}*/
var _this = this;
return function () {
var i = Math.floor(Math.random() * 4);
return {
n: _this.name[i] //m*
};
};
}
};
var Myname = people.getName();
alert("名字:" + Myname().n);

5.重载

function attr(name:string):string;
function attr(age:number):number;

function attr(nameorage:any):any{
if(nameorage&&typeof nameorage == "string"){
alert("name");
}else{
alert("age");
}

}

//attr("mm");//name
attr(11);//age

function attr(nameorage) {
if (nameorage && typeof nameorage == "string") {
alert("name");
}
else {
alert("age");
}
}
//attr("mm");//name
attr(11); //age