[英]Javascript - Finding in subarray by value from another array
我有兩個JavaScript對象:
var classroom = {
"number" : "1",
"student" : [
{
"number" : 1,
"items" : [
{
"key" : "00000000000000000000001C",
"date" : "2016-04-21T17:35:39.997Z"
}
]
},
{
"number" : 2,
"items" : [
{
"key" : "00000000000000000000001D",
"date" :"2016-04-21T17:35:39.812Z"
},
{
"key" : "00000000000000000000002N",
"date" :"2016-04-21T17:35:40.159Z"
},
{
"key" : "00000000000000000000002Ñ",
"date" :"2016-04-21T17:35:42.619Z"
}
]
}
],
}
和
var items = [
{
"fields" : {
"tags" : [
{
"key" : "00000000000000000000001C",
"Batch" : "50",
"Bin" : "01",
"Tray" : "02"
},
{
"key" : "00000000000000000000002N",
"Batch" : "55",
"Bin" : "05",
"Tray" : "12"
},
{
"key" : "000000000000228510000032",
"Batch" : "12",
"Bin" : "12",
"Tray" : "01"
}
],
"Name" : "Rubber"
},
"_id" : "56d19b48faa37118109977c0"
},
{
"fields" : {
"tags" : [
{
"key" : "00000000000000000000001D",
"Batch" : "50",
"Bin" : "01",
"Tray" : "05"
},
{
"key" : "00000000000000000000002Ñ",
"Batch" : "52",
"Bin" : "07",
"Tray" : "02"
},
{
"key" : "221567010000000000000089",
"Batch" : "11",
"Bin" : "15",
"Tray" : "03"
}
],
"Name" : "Book"
},
"_id" : "56d19b48faa37118109977c1"
}
];
好的,我需要創建一個遍歷classroom
變量中每個student
每個item
的函數。 對於每個item
,我需要在items
數組中找到在其tags
之一中具有完全相同的key
的對象。
我的代碼得到了奇怪的結果...項目不匹配...
var finalitems = [];
classroom.student.forEach( function (student){
student.items.forEach( function (obj){
items.forEach( function (theitem){
theitem.fields.tags.forEach( function (tag){
if (tag.key === obj.key) {
var newitem = theitem;
newitem.tag = obj;
finalitems.push(newitem);
}
});
});
});
});
我知道foreach是一種指針,但是我真的不明白為什么它會奇怪地工作以及應該如何做。
問候,
javascript變量僅保存對象引用,而不保存內存中的實際對象,因此此行:
var newitem = theitem;
表示newitem與theitem引用同一對象,而不是從theitem創建新對象。
所以
newitem.tag = obj;
是相同的
theitem.tag = obj;
這意味着您正在修改輸入對象,這就是為什么您將無法獲得預期輸出的原因。
要獲得所需的行為,您需要創建theitem的副本並將該對象分配給newitem變量:
var newitem = Object.create(theitem);
也許這有助於進行更多的迭代。
var classroom = { "number": "1", "student": [{ "number": 1, "items": [{ "key": "00000000000000000000001C", "date": "2016-04-21T17:35:39.997Z" }] }, { "number": 2, "items": [{ "key": "00000000000000000000001D", "date": "2016-04-21T17:35:39.812Z" }, { "key": "00000000000000000000002N", "date": "2016-04-21T17:35:40.159Z" }, { "key": "00000000000000000000002Ñ", "date": "2016-04-21T17:35:42.619Z" }] }] }, items = [{ "fields": { "tags": [{ "key": "00000000000000000000001C", "Batch": "50", "Bin": "01", "Tray": "02" }, { "key": "00000000000000000000002N", "Batch": "55", "Bin": "05", "Tray": "12" }, { "key": "000000000000228510000032", "Batch": "12", "Bin": "12", "Tray": "01" }], "Name": "Rubber" }, "_id": "56d19b48faa37118109977c0" }, { "fields": { "tags": [{ "key": "00000000000000000000001D", "Batch": "50", "Bin": "01", "Tray": "05" }, { "key": "00000000000000000000002Ñ", "Batch": "52", "Bin": "07", "Tray": "02" }, { "key": "221567010000000000000089", "Batch": "11", "Bin": "15", "Tray": "03" }], "Name": "Book" }, "_id": "56d19b48faa37118109977c1" }], finalitems = []; classroom.student.forEach(function (student) { student.items.forEach(function (studentItem) { items.forEach(function (item) { item.fields.tags.forEach(function (itemTag) { if (itemTag.key === studentItem.key) { finalitems.push({ key: studentItem.key, date: studentItem.date, Batch: itemTag.Batch, Bin: itemTag.Bin, Tray: itemTag.Tray, }); } }); }); }); }); document.write('<pre>' + JSON.stringify(finalitems, 0, 4) + '</pre>');
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