<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>扩展运算符</title>
</head>
<body>
<script>
/*
扩展运算符（spread）是三个点（...）。
它好比 rest 参数的逆运算，将一个数组转为用逗号分隔的参数序列。
*/
function sum(...numbers){
return numbers
}
console.log(sum(1,3,9))//[1, 3, 9]
//reduce() 方法对数组中的每个元素执行一个由您提供的reducer函数(升序执行)，将其结果汇总为单个返回值。
function sum1(...numbers){
return numbers.reduce((prev,curr)=>{
console.log(`prev:${prev},curr:${curr}`)//prev:1,curr:3 prev:4,curr:9
return prev+curr
})
}
console.log(sum1(1,3,9))//13
/*
场景练习：汇率或者乘法表
运用到：扩展运算符（...）和map映射
*/
function exchangeRate(rate,...amounts){
console.log(rate,amounts)//100 (3) [14.56, 1571.45, 16830.01]
return amounts.map(amount=>{
return amount*rate
})
}
console.log(exchangeRate(100,14.56,1571.45,16830.01))//(3) [1456, 157145, 1683000.9999999998]
/*
变量的结构
*/
const player=['xyz',12,23,56,34,7,8]
const[name1,id1,scores1]=player
console.log(name1,id1,scores1)//xyz 12 23
const [name,id,...scores]=player
console.log(name,id,scores)//xyz 12 (5) [23, 56, 34, 7, 8]
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>扩展运算符1</title>
</head>
<body>
<script>
const youngers = ['小红', '小明'];
const olders = ['张三', '李四'];
/*
将youngers数组和olders数组进行整合：
['小红', '小明'，'张三', '李四']。
*/
//JS方法
// concat() 方法用于合并两个或多个数组。此方法不会更改现有数组，而是返回一个新数组。
const members = youngers.concat(olders)
console.log(members)//["小红", "小明", "张三", "李四"]
/*
注意现在我想在这两个数组：youngers数组和olders数组进行整合后
在里面加个名字['小红', '小明'，'小强'，'张三', '李四']。
*/
// ES5
let members1 = [];
members1 = members1.concat(youngers);
members1.push('小强');
members1 = members1.concat(olders);
console.log(members1);//(5) ["小红", "小明", "小强", "张三", "李四"]
//ES6
const members2 = [...youngers, '小强', ...olders];
console.log(members2);["小红", "小明", "小强", "张三", "李四"]
/*
注意现在问题继续延伸：我想在这两个数组：youngers数组和olders数组进行整合后
在里面加个名字['小红', '小明'，'小强'，'张三', '李四']，并且修改第一个名字小红，
而不影响整合后加名字的数组：
*/
//失败的操作
const members3 = [...youngers, '小强', ...olders];
const members4=members3;
members4[0]='小东';
console.log(members3);//(5) ["小东", "小明", "小强", "张三", "李四"]
console.log(members4);//(5) ["小东", "小明", "小强", "张三", "李四"]
//成功的操作
const members5 = [...youngers, '小强', ...olders];
const members6=[...members5];
members6[0]='小东';
console.log(members5);//(5) ["小红", "小明", "小强", "张三", "李四"]
console.log(members6);//(5) ["小东", "小明", "小强", "张三", "李四"]
</script>
</body>
</html>