MongoDB objects are object Id of another document stored in the mongo database. We can place multiple objects using list of object fields. A sample mongo object list as follows.
"tags": [
{
"posts": [
"5fef1f5087a69346300003a7"
],
"_id": "5fef1f5187a69346300003a8",
"tagName": "Test",
"createdAt": "2021-01-01T13:10:41.799Z",
"updatedAt": "2021-01-01T13:10:41.855Z",
"__v": 1
},
{
"posts": [
"5fef1f5087a69346300003a7"
],
"_id": "5fef1f5187a69346300003a9",
"tagName": "VM",
"createdAt": "2021-01-01T13:10:41.804Z",
"updatedAt": "2021-01-01T13:10:41.896Z",
"__v": 1
},
{
"posts": [
"5fef1f5087a69346300003a7",
"5fef1f7287a69346300003af"
],
"_id": "5fef1f5187a69346300003aa",
"tagName": "JS",
"createdAt": "2021-01-01T13:10:41.810Z",
"updatedAt": "2021-01-01T13:11:15.561Z",
"__v": 2
}
],
We want to lookup at the above list of tags and make sure no more duplicate tags shown up in the future. A loop will do the job, using a filter we can do the same.
if (post.tags.filter(xtag => xtag == 'ABCD') == false) {
console.log(`No Tag found`);
} else {
console.log(`Tag already added`);
}
The filter uses a quick arrow function to filter result and return false when it failed to match the tag.
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