<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>形参和实参</title>
</head>
<body>
</body>
<script>
function sum(a,b){
return a+b;
}
//实参个数可以比形参个数多，反之不行；
console.log(sum());//NaN
console.log(sum(1));//NaN
console.log(sum(1,2,3,6));//3
</script>
</html>
<html>
<head>
<meta charset="utf-8">
<title>默认参数</title>
</head>
<body>
</body>
<script>
//旧版js中默认参数赋值
function avg(total,year){
year=year||1;
return Math.round(total/year);
}
console.log(avg(3000,3));//1000
console.log(avg(3000));//3000
//新版js
function average(total,year=1){
return Math.round(total/year);
}
console.log(average(3000));//3000
console.log(average(3000,3));
//数组排序
function sortArray(array,type="asc"){
return array.sort(function(a,b){
return type=="asc"?a-b:b-a;
});
}
console.log(sortArray([3,2,1,4,5]));// [1, 2, 3, 4, 5]
//折扣函数,注意默认参数放在后面，函数调用时会按顺序赋予形参值
function sum(total,discount=1,dis=1){
return total*discount*dis;
}
console.log(sum(2000,0.9));
</script>
</html>
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