排除反向引用
重要性: 5
在简单的循环引用情况下，我们可以通过名称排除序列化中出现问题的属性。
但有时我们不能只使用名称，因为它可能同时用于循环引用和普通属性。因此，我们可以通过其值来检查属性。
编写 replacer 函数来将所有内容字符串化，但删除引用 meetup 的属性。
let room = {
number: 23
};
let meetup = {
title: "Conference",
occupiedBy: [{name: "John"}, {name: "Alice"}],
place: room
};
// circular references
room.occupiedBy = meetup;
meetup.self = meetup;
alert( JSON.stringify(meetup, function replacer(key, value) {
/* your code */
}));
/* result should be:
{
"title":"Conference",
"occupiedBy":[{"name":"John"},{"name":"Alice"}],
"place":{"number":23}
}
*/let room = {
number: 23
};
let meetup = {
title: "Conference",
occupiedBy: [{name: "John"}, {name: "Alice"}],
place: room
};
room.occupiedBy = meetup;
meetup.self = meetup;
alert( JSON.stringify(meetup, function replacer(key, value) {
return (key != "" && value == meetup) ? undefined : value;
}));
/*
{
"title":"Conference",
"occupiedBy":[{"name":"John"},{"name":"Alice"}],
"place":{"number":23}
}
*/这里我们还需要测试 key=="" 以排除第一次调用，因为在这种情况下 value 为 meetup 是正常的。