JavaScript - Array and Nested Objects

Question

I have an API call that returns the following JSON:

{
"name": "Ethereum 2.0",
"symbol": "ETH",
"slug": "ethereum-2-0",
"meta": {
    "start": "2022-08-03T02:43:56Z",
    "startTimestamp": 1659494636000000000,
    "end": "2022-08-04T02:43:56Z",
    "endTimestamp": 1659581036000000000
},
"data": [{
        "timestamp": 1659579311,
        "totalStaked": 10.795673641155977,
        "engagedBalance": 13151223,
        "inflation": 0.49479127486939656,
        "rewardOptions": [{
                "Name": "Run a Validator",
                "Reward": 4.583236686436322,
                "AdjustedReward": 4.068315740250017
            },
            {
                "Name": "Validator-as-a-Service",
                "Reward": 3.7811702663099656,
                "AdjustedReward": 3.2701983354060715
            },
            {
                "Name": "Exchange Staking",
                "Reward": 3.899917762276725,
                "AdjustedReward": 3.388361171967369
            }]
        },
        {
        "timestamp": 1659572709,
        "totalStaked": 10.795673641155977,
        "engagedBalance": 13151223,
        "inflation": 0.49479127486939656,
        "rewardOptions": [{
                "Name": "Run a Validator",
                "Reward": 4.583236686436322,
                "AdjustedReward": 4.068315740250017
            },
            {
                "Name": "Validator-as-a-Service",
                "Reward": 3.7811702663099656,
                "AdjustedReward": 3.2701983354060715
            },
            {
                "Name": "Exchange Staking",
                "Reward": 3.899917762276725,
                "AdjustedReward": 3.388361171967369
            }]
        }
    ] 
}

I am trying to flatten the "data" array in Javascript to create the following outcome:

[{
"timestamp": 1659579311,
"totalStaked": 10.795673641155977,
"engagedBalance": 13151223,
"inflation": 0.49479127486939656,
"rewardOptions[0].Name": "Run a Validator",
"rewardOptions[0].Reward": 4.583236686436322,
"rewardOptions[0].AdjustedReward": 4.068315740250017,
"rewardOptions[1].Name": "Validator-as-a-Service",
"rewardOptions[1].Reward": 3.7811702663099656,
"rewardOptions[1].AdjustedReward": 3.2701983354060715,
"rewardOptions[2].Name": "Exchange Staking",
"rewardOptions[2].Reward": 3.899917762276725,
"rewardOptions[2].AdjustedReward": 3.388361171967369
},{
"timestamp": 1659572709,
"totalStaked": 10.795673641155977,
"engagedBalance": 13151223,
"inflation": 0.49479127486939656,
"rewardOptions[0].Name": "Run a Validator",
"rewardOptions[0].Reward": 4.583236686436322,
"rewardOptions[0].AdjustedReward": 4.068315740250017,
"rewardOptions[1].Name": "Validator-as-a-Service",
"rewardOptions[1].Reward": 3.7811702663099656,
"rewardOptions[1].AdjustedReward": 3.2701983354060715,
"rewardOptions[2].Name": "Exchange Staking",
"rewardOptions[2].Reward": 3.899917762276725,
"rewardOptions[2].AdjustedReward": 3.388361171967369
}]

I have tried every .map, .flat, .forEach variety I can find, as well as about 30 different solutions I've found on Stack Overflow to flatten JSON responses (over the past 6 hours), but they'll either flatten the first 4 "data" keys and leave "rewardOptions" as an array of objects or create some other outcome other than what I'm wanting to achieve. The data is going to be displayed in a table, so I need the final result to be an array of objects so everything displays properly. Any help to get me unstuck would be greatly appreciated.

Update 1:

Here's the code for the closest-to-a-working version I had:

var data = {{ querysubmit.data.data }}

function flatten(array) {
    var result = [];
    array.forEach(function iter(o) {
        var temp = {},
            keys = Object.keys(o);

        if (keys.length > 1) {
            keys.forEach(function (k) {
                if (k !== 'rewardOptions') {
                    temp[k] = o[k];
                }
            });
            temp.rewardType1 = o.rewardOptions[0].Name;
            temp.rewardRate1 = o.rewardOptions[0].Reward;
            temp.adjustedRewardRate1 = o.rewardOptions[0].AdjustedReward;
            temp.rewardType2 = o.rewardOptions[1].Name;
            temp.rewardRate2 = o.rewardOptions[1].Reward;
            temp.adjustedRewardRate2 = o.rewardOptions[1].AdjustedReward;
            temp.rewardType3 = o.rewardOptions[2].Name;
            temp.rewardRate3 = o.rewardOptions[2].Reward;
            temp.adjustedRewardRate3 = o.rewardOptions[2].AdjustedReward;
            result.push(temp);
        }
        Array.isArray(o.data) && o.temp.forEach(iter);
    });
    return result;
}

return flatten(data)

}

I imagine myObject.data.map(some_deeply_recursive_function) — qrsngky
– qrsngky, Commented Aug 4, 2022 at 3:49
Add some code for things you've tried - SO users generally appreciate when you show that you've put in an effort. It's usually easier to work from broken code than from scratch, and as the person asking the question you'll probably learn more too — Codebling
– Codebling, Commented Aug 4, 2022 at 3:51

Nairi Abgaryan · Accepted Answer · 2022-08-04 04:40:32Z

If this is just a case, you can make your algorithm for the flatting array.

Here is one way to make that using loops.

const arr = {
    "name": "Ethereum 2.0",
    "symbol": "ETH",
    "slug": "ethereum-2-0",
    "meta": {
        "start": "2022-08-03T02:43:56Z",
        "startTimestamp": 1659494636000000000,
        "end": "2022-08-04T02:43:56Z",
        "endTimestamp": 1659581036000000000
    },
    "data": [{
        "timestamp": 1659579311,
        "totalStaked": 10.795673641155977,
        "engagedBalance": 13151223,
        "inflation": 0.49479127486939656,
        "rewardOptions": [{
            "Name": "Run a Validator",
            "Reward": 4.583236686436322,
            "AdjustedReward": 4.068315740250017
        },
            {
                "Name": "Validator-as-a-Service",
                "Reward": 3.7811702663099656,
                "AdjustedReward": 3.2701983354060715
            },
            {
                "Name": "Exchange Staking",
                "Reward": 3.899917762276725,
                "AdjustedReward": 3.388361171967369
            }]
    },
        {
            "timestamp": 1659572709,
            "totalStaked": 10.795673641155977,
            "engagedBalance": 13151223,
            "inflation": 0.49479127486939656,
            "rewardOptions": [{
                "Name": "Run a Validator",
                "Reward": 4.583236686436322,
                "AdjustedReward": 4.068315740250017
            },
                {
                    "Name": "Validator-as-a-Service",
                    "Reward": 3.7811702663099656,
                    "AdjustedReward": 3.2701983354060715
                },
                {
                    "Name": "Exchange Staking",
                    "Reward": 3.899917762276725,
                    "AdjustedReward": 3.388361171967369
                }]
        }
    ]
}

let data = arr.data
let res = []
for(let i = 0; i < data.length; i++){
     const objKeys = Object.keys(data[i]);
     let obj = {}

    for (let j = 0; j < objKeys.length; j++){
            if(Array.isArray(data[i][objKeys[j]])){
                 flatArray(data[i][objKeys[j]], objKeys[j], obj)
            } else {
                const key = objKeys[j]
                obj[key] = data[i][objKeys[j]]
            }
     }

    res.push(obj)
}

function flatArray(arr, parentKey, res){
    for (let j = 0; j < arr.length; j++){
        const objKeys = Object.keys(arr[j]);
        for(let i = 0; i < objKeys.length; i++){
            const key = `${parentKey}[${j}].${objKeys[i]}`
            res[key] = arr[j][objKeys[i]]
        }
    }

    return res
}

console.log(res)

NOTE: "this solution will not work in case of different level nested arrays"

This worked perfectly in Retool (the platform in which I'm building my application). Thank you so much for answering, I can finally get some sleep! :)

qrsngky · Accepted Answer · 2022-08-04 04:14:33Z

So for every entry in myObject.data, you should make a new object, and recursively add values to that new object.

let myObject = {
    "name": "Ethereum 2.0",
    "symbol": "ETH",
    "slug": "ethereum-2-0",
    "meta": {
        "start": "2022-08-03T02:43:56Z",
        "startTimestamp": 1659494636000000000,
        "end": "2022-08-04T02:43:56Z",
        "endTimestamp": 1659581036000000000
    },
    "data": [{
        "timestamp": 1659579311,
        "totalStaked": 10.795673641155977,
        "engagedBalance": 13151223,
        "inflation": 0.49479127486939656,
        "rewardOptions": [{
            "Name": "Run a Validator",
            "Reward": 4.583236686436322,
            "AdjustedReward": 4.068315740250017
        },
        {
            "Name": "Validator-as-a-Service",
            "Reward": 3.7811702663099656,
            "AdjustedReward": 3.2701983354060715
        },
        {
            "Name": "Exchange Staking",
            "Reward": 3.899917762276725,
            "AdjustedReward": 3.388361171967369
        }]
    },
    {
        "timestamp": 1659572709,
        "totalStaked": 10.795673641155977,
        "engagedBalance": 13151223,
        "inflation": 0.49479127486939656,
        "rewardOptions": [{
            "Name": "Run a Validator",
            "Reward": 4.583236686436322,
            "AdjustedReward": 4.068315740250017
        },
        {
            "Name": "Validator-as-a-Service",
            "Reward": 3.7811702663099656,
            "AdjustedReward": 3.2701983354060715
        },
        {
            "Name": "Exchange Staking",
            "Reward": 3.899917762276725,
            "AdjustedReward": 3.388361171967369
        }]
    }
    ]
}


function recursiveAddProp(sourceObj, targetObj, keyPrefix) {
    if (Array.isArray(sourceObj)) {
        for (let i = 0; i < sourceObj.length; i++) {
            recursiveAddProp(sourceObj[i], targetObj, keyPrefix + `[${i}]`);
        }
    } else if (typeof sourceObj === 'object' && sourceObj !== null) {
        for (let key in sourceObj) {
            recursiveAddProp(sourceObj[key], targetObj, keyPrefix === '' ? key : keyPrefix + '.' + key)
        }
    } else {
        targetObj[keyPrefix] = sourceObj;
    }
}
const flattener = (data_entry) => {
    let newObj = {}
    recursiveAddProp(data_entry, newObj, '')
    return newObj;
}
let flattenedObject = myObject.data.map(flattener);

console.log(JSON.stringify(flattenedObject))

Beautified output:

[{
    "timestamp": 1659579311,
    "totalStaked": 10.795673641155977,
    "engagedBalance": 13151223,
    "inflation": 0.49479127486939656,
    "rewardOptions[0].Name": "Run a Validator",
    "rewardOptions[0].Reward": 4.583236686436322,
    "rewardOptions[0].AdjustedReward": 4.068315740250017,
    "rewardOptions[1].Name": "Validator-as-a-Service",
    "rewardOptions[1].Reward": 3.7811702663099656,
    "rewardOptions[1].AdjustedReward": 3.2701983354060715,
    "rewardOptions[2].Name": "Exchange Staking",
    "rewardOptions[2].Reward": 3.899917762276725,
    "rewardOptions[2].AdjustedReward": 3.388361171967369
}, {
    "timestamp": 1659572709,
    "totalStaked": 10.795673641155977,
    "engagedBalance": 13151223,
    "inflation": 0.49479127486939656,
    "rewardOptions[0].Name": "Run a Validator",
    "rewardOptions[0].Reward": 4.583236686436322,
    "rewardOptions[0].AdjustedReward": 4.068315740250017,
    "rewardOptions[1].Name": "Validator-as-a-Service",
    "rewardOptions[1].Reward": 3.7811702663099656,
    "rewardOptions[1].AdjustedReward": 3.2701983354060715,
    "rewardOptions[2].Name": "Exchange Staking",
    "rewardOptions[2].Reward": 3.899917762276725,
    "rewardOptions[2].AdjustedReward": 3.388361171967369
}]

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