在与 ES6 深度嵌套的对象的 javascript 数组中查找值

Question

In an array of objects I need to find a value -- where key is activity : However the activity key can be deeply nested in the array like so:

const activityItems = [
    {
        name: 'Sunday',
        items: [
            {
                name: 'Gym',
                activity: 'weights',
            },
        ],
    },
    {
        name: 'Monday',
        items: [
            {
                name: 'Track',
                activity: 'race',
            },
            {
                name: 'Work',
                activity: 'meeting',
            },
            {
                name: 'Swim',
                items: [
                    {
                        name: 'Beach',
                        activity: 'scuba diving',
                    },
                    {
                        name: 'Pool',
                        activity: 'back stroke',
                    },
                ],
            },
        ],    
    },
    {} ...
    {} ...
];

So I wrote a recursive algorithm to find out if a certain activity is in the array:

let match = false;
const findMatchRecursion = (activity, activityItems) => {
    for (let i = 0; i < activityItems.length; i += 1) {
        if (activityItems[i].activity === activity) {
            match = true;
            break;
        }

        if (activityItems[i].items) {
            findMatchRecursion(activity, activityItems[i].items);
        }
    }

    return match;
};

Is there an ES6 way of determining if an activity exists in an array like this?

I tried something like this:

const findMatch(activity, activityItems) {
    let obj = activityItems.find(o => o.items.activity === activity);
    return obj;
}

But this won't work with deeply nested activities.

Thanks

Answer 1

You can use some() method and recursion to find if activity exists on any level and return true/false as result.

 const activityItems = [{"name":"Sunday","items":[{"name":"Gym","activity":"weights"}]},{"name":"Monday","items":[{"name":"Track","activity":"race"},{"name":"Work","activity":"meeting"},{"name":"Swim","items":[{"name":"Beach","activity":"scuba diving"},{"name":"Pool","activity":"back stroke"}]}]}] let findDeep = function(data, activity) { return data.some(function(e) { if(e.activity == activity) return true; else if(e.items) return findDeep(e.items, activity) }) } console.log(findDeep(activityItems, 'scuba diving'))

Answer 2

While not as elegant as a recursive algorithm, you could JSON.stringify() the array, which gives this:

[{"name":"Sunday","items":[{"name":"Gym","activity":"weights"}]},{"name":"Monday","items":[{"name":"Track","activity":"race"},{"name":"Work","activity":"meeting"},{"name":"Swim","items":[{"name":"Beach","activity":"scuba diving"},{"name":"Pool","activity":"back stroke"}]}]}]

You could then use a template literal to search for the pattern:

`"activity":"${activity}"`

Complete function:

findMatch = (activity, activityItems) =>
  JSON.stringify(activityItems).includes(`"activity":"${activity}"`);

 const activityItems = [{ name: 'Sunday', items: [{ name: 'Gym', activity: 'weights', }, ], }, { name: 'Monday', items: [{ name: 'Track', activity: 'race', }, { name: 'Work', activity: 'meeting', }, { name: 'Swim', items: [{ name: 'Beach', activity: 'scuba diving', }, { name: 'Pool', activity: 'back stroke', }, ], }, ], } ]; findMatch = (activity, activityItems) => JSON.stringify(activityItems).includes(`"activity":"${activity}"`); console.log(findMatch('scuba diving', activityItems)); //true console.log(findMatch('dumpster diving', activityItems)); //false

Answer 3

First, your function could be improved by halting once a match is found via the recursive call. Also, you're both declaring match outside, as well as returning it. Probably better to just return.

const findMatchRecursion = (activity, activityItems) => {
    for (let i = 0; i < activityItems.length; i += 1) {
        if (activityItems[i].activity === activity) {
            return true;
        }

        if (activityItems[i].items && findMatchRecursion(activity, activityItems[i].items) {
            return true;
        }
    }

    return false;
};

There's no built in deep search, but you can use .find with a named function if you wish.

var result = !!activityItems.find(function fn(item) {
  return item.activity === "Gym" || (item.items && item.items.find(fn));
});

Answer 4

We now use object-scan for simple data processing tasks like this. It's really good once you wrap your head around how to use it. Here is how one could answer your questions

 // const objectScan = require('object-scan'); const find = (activity, input) => objectScan(['**'], { abort: true, rtn: 'value', filterFn: ({ value }) => value.activity === activity })(input); const activityItems = [{"name":"Sunday","items":[{"name":"Gym","activity":"weights"}]},{"name":"Monday","items":[{"name":"Track","activity":"race"},{"name":"Work","activity":"meeting"},{"name":"Swim","items":[{"name":"Beach","activity":"scuba diving"},{"name":"Pool","activity":"back stroke"}]}]}] console.log(find('scuba diving', activityItems)); // => { name: 'Beach', activity: 'scuba diving' }

 .as-console-wrapper {max-height: 100% !important; top: 0}

 <script src="https://bundle.run/object-scan@13.8.0"></script>

Disclaimer : I'm the author of object-scan