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

Question

好的，所以我浏览了 Record Collection 教程，并对原始挑战有了非常深入的了解。 但是，如果集合不存在，我希望我的函数能够将新 ID 添加到集合中。 我尝试了很多变体，但我不知道该怎么做（菜鸟-_-）。 我知道这不是必需的，但我认为这将有助于我对对​​象和数组的整体理解。

下面的代码是我最近的尝试。 第一个 if 语句是我的附加组件。 我应该先用 .hasOwnProperty 运行 if 语句吗？ 同上。 请用虚词解释。 :)

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

如果您试图在将记录添加到集合之前确保该记录不存在，最简单的方法是使用类似Array.find 。

下面的代码只检查id字段以查看它是否已经存在。 在您的场景中，您可能想要检查其他属性，因此您的.find将进行一些额外的检查。

例子：

 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

使用object集合而不是objects array的示例

 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

另一种方法：

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