排除反向引用
返回課程
重要性：5
在循環引用的簡單情況下，我們可以透過名稱從序列化中排除有問題的屬性。
但有時候我們不能只使用名稱，因為它可能同時用於循環引用和一般屬性中。因此，我們可以透過其值來檢查屬性。
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}
}
*/在此我們也需要測試 key=="" 以排除第一次呼叫，在第一次呼叫中 value 為 meetup 是正常的。