在我之前有关使用map（）的一篇文章中，使用标准if / else块解决了该问题。但是现在我有另一个问题。这是使用if / else的解决方案：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Transforming Data</title>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<h1>Transforming Data</h1>
<p>Open the console</p>
<script type="text/babel">
// Editing one object in an array of objects
let schools = [
{name: 'Yorktown'},
{name: 'Stratford'},
{name: 'Washington & Lee'},
{name: 'Wakefield'}
];
const editName = (oldName, newName, arr) =>
arr.map(item => {
if (item.name === oldName) {
return {
...item,
name: newName
}
}
else {
return item
}
});
let updatedSchools = editName('Stratford', 'HB Woodlawn', schools);
console.log(updatedSchools[1]); // {name: "HB Woodlawn"}
console.log(schools[1]); // {name: "Stratford"}
</script>
</body>
</html>
但是，使用功能箭头时不想为我工作。映射时不会进行替换。但是，我使用的是相同的解决方案-即：“名称：名称”。我究竟做错了什么？
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Transforming Data</title>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<h1>Transforming Data</h1>
<p>Open the console</p>
<script type="text/babel">
let schools = [
'Yorktown',
'Stratford',
'Washington & Lee',
'Wakefield'
];
const editName = (oldName, name, arr) =>
arr.map(item => (item.name === oldName) ?
({...item, name: name}) :
item
);
let updatedSchools = editName('Stratford', 'HB Woodlawn', schools);
console.log(updatedSchools[1]); // Stratford
console.log(schools[1]); // Stratford
</script>
</body>
</html>
最佳答案
您的新数组是字符串数组，而不是对象数组，因此没有name属性，这意味着item.name将始终返回undefined。
如果要继续使用字符串数组，则必须像下面这样修改函数：
let schools = [
'Yorktown',
'Stratford',
'Washington & Lee',
'Wakefield'
];
const editName = (oldName, name, arr) =>
arr.map(item => (item === oldName) ? name : item);
let updatedSchools = editName('Stratford', 'HB Woodlawn', schools);
console.log(updatedSchools[1]); // Stratford
console.log(schools[1]); // Stratford