JavaScript関数とjs匿名関数の注意点まとめ_JavaScriptスキル

function functionName(arg0,arg1,...,argN) {
 statements
}

function str(name,age){
 document.write("hello my name is " + name + ". and i am " + age + " years old.");
}
str(" oliver",23); //hello my name is oliver. and i am 23 years old.

function sum(num1,num2){
 return num1 + num2;
 alert("hello"); //返回return 之后不会继续执行alert
}
var result = sum(321,32);
document.write(result); //353

function conp(a,b){
 if (a > b){
 return a;
 }else if (a == b){
 return "equal";
 }else{
 return b;
 }
}
var result = conp(4,4);
document.write(result); //equal
var result = conp(321,4);
document.write(result); //321

function conp(a,b){
 if (a > b){
 return;
 document.write("bad");
 }else{
 document.write(b);
 }
}
var a = conp(33,3);
document.write(a); //返回undefined 且不会出现"bad"

function greeting(){
 document.write("hello " + arguments[0] + ". you look " + arguments[1] + ".");
}
greeting("oliver","good"); //hello oliver. you look good.

function countArguments(){
 document.write("there are " + arguments.length + " arguments here.");
}
countArguments(321,321,32,32); //there are 4 arguments here.

function count(){
 if (arguments.length == 1){
 document.write("you just have 1 arguments.");
 }else{
 document.write("you have many arguments.");
 }
}
count(321,321,321) //you have many arguments.

function add(){
 document.write(arguments[0] + arguments[1]);
}
function add(){
 document.write(arguments[0] + 100);
}
add(321,2); //421 不会执行第一个函数（两个参数相加），只执行最后一个同名的函数（第一个参数加上100）

function double(x){
 return 2 * x; 
}

(function(x, y){
 alert(x + y); 
})(2, 3);