我想加入来自 freeCodeCamp 的 Record Collection 挑战，但我被卡住了

Question

Ok, so I went through the Record Collection tutorial and have a pretty solid understanding of the original challenge. However, I want my function to be able to add a new ID to the collection if it doesn't already exist. I've tried so many variations, and I can't figure out how to do that (noob -_-). I know this isn't necessary, but I think this will help with my overall understanding of objects and arrays anyway.

Code below is my latest attempt. The first if statement is my add-on. Should I be running an if statement with .hasOwnProperty first? Idk. Please explain in dummy terms. :)

var collection = {
    2548: {
        album: "Slippery When Wet",
        artist: "Bon Jovi",
        tracks: [
            "Let It Rock",
            "You Give Love a Bad Name"
        ]
    },
    2468: {
        album: "1999",
        artist: "Prince",
        tracks: [
            "1999",
            "Little Red Corvette"
        ]
    },
    1245: {
        artist: "Robert Palmer",
        tracks: []
    },
    5439: {
        album: "ABBA Gold"
    }
};

function updateRecords(id, prop, value) {

// If the id is not blank and the prop is not blank,
    if (id !== "" && prop !== "") {

// then create the new id name and push the property onto it.
        collection.id = [];
        collection[id].push(prop);
    }

//If the property is equal to "tracks" and the tracks value isn't empty,
    else if (value !== "" && prop === "tracks") {

//update or set the value for the property.
        collection[id][prop].tracks;

//If the specificied id doesn't have the property tracks,
    } else if (!collection[id].hasOwnProperty("tracks")) {

//then add the property tracks and push in the track's name value       
        collection[id].tracks = [];
        collection[id].tracks.push(value);

//Otherwise delete the id entirely.
    } else {

    delete collection[id][prop];
    }

    return collection;
}

updateRecords(2005, "tracks", "check on it");

Answer 1

If you are trying to make sure a record doesn't exist before adding it to a collection, the easiest way to do it is to use something like Array.find .

The below code only checks the id field to see if it already exists. In your scenario, you may want to check other properties, so your .find will have some extra checks.

Example:

 const records = [ { id: 1, name: 'Test1' }, { id: 2, name: 'Test2' }, { id: 3, name: 'Test3' }, { id: 4, name: 'Test4' }, ]; const addRecord = (record) => { if (record) { const existingRecord = records.find(r => r.id === record.id); if (existingRecord) { return `Record ${record.id} already exists`; } records.push(record); return records; } return 'Record cannot be falsy'; } console.log(addRecord({ id: 5, name: 'Test5' })); // Adds record console.log(addRecord({ id: 1, name: 'Test123123123 doesnt matter' })); // Record already exists

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find

Example with object collection instead of array of objects

 let records = { 1: { name: 'Test1' }, 2: { name: 'Test2' }, 3: { name: 'Test3' }, 4: { name: 'Test4' } }; const findRecord = (recordId) => { for(const key in records) { if (+key === recordId) return records[key]; } return null; }; const addRecord = (id, name) => { if (id && name) { const recordExists = findRecord(id); if (recordExists) return `Record ${id} already exists`; records[id] = { name }; return records; } return 'Record cannot be falsy'; }; console.log(addRecord(5, 'Test5')); // Adds record console.log(addRecord(1, 'blag asdfsdafafds')); // Already exists

Answer 2

Another way to do it:

let records = {
    1: { name: 'Test1' },
    2: { name: 'Test2' },
    3: { name: 'Test3' },
    4: { name: 'Test4' }
}

const addRecord = (id, name) => {
    if (!id || !name) {
        return 'Id and name must be defined'
    }

    const exists = Object.keys(records).some(recordId => +recordId === id)

    if (exists) {
        return `${id} already exists`
    }

    records[id] = { name }

    return records
}

console.log(addRecord(5, 'Test5')) // Adds record
console.log(addRecord(1, 'blag asdfsdafafds')) // Already exists