Javascript/Typescript: Best way to append value in object based on condition from other object

Question

Updated object keys

    let conditionedObject = {
        "isNameRequired": true,
        "isCityRequired": false,
        "isPostRequired": true
    };
    
    let myTotalData = {
     data: {
        "givenName": 'myname',
        "street":"mystreet",
        "cityName": 'mycity',
        "postcode": 'mypost'
      }
    };

let resultData = {};

Both condionedObject and myTotalData comes from different source. I would like to know the best way to create a new object based on the condionedObject, example my condionedObject says I need only name and post so my resultData should return {"givenName":"myname","postcode":"mypost"}

conditionedObject.isNameRequired is for myTotalData.data.givenName, conditionedObject.isPostRequired is for myTotalData.data.postcode, conditionedObject.isCityRequired is for myTotalData.data.cityName, all this will say whether myTotalData key is required to be placed in the new object.

Thanks in advance for all the suggestions and helps

All, The data of objects conditionedObject and myTotalData comes from different sources I gave sample key names, consider removing "is" from key names are not an option. consider them as isNameRequired, isCityRequired, isPostRequired..etc — sunilsmith
– sunilsmith, Commented Nov 5, 2020 at 11:55

lissettdm · Accepted Answer · 2020-11-05 12:15:13Z

1

You can use Array.prototype.reduce():

In this case I recommend you to create a new object to store the relationship between properties:

  

  let conditionedObject = {
  "isNameRequired": true,
  "isCityRequired": false,
  "isPostRequired": true
};

let myTotalData = {
  data: {
    "givenName": 'myname',
    "street":"mystreet",
    "cityName": 'mycity',
    "postcode": 'mypost'
  }
};

const reference = {
  "isNameRequired": "givenName",
  "isCityRequired": "cityName",
  "isPostRequired": "postcode"
}

let resultData = {};

resultData =Object.entries(conditionedObject).reduce((obj, [key, value]) => {
   if(value && myTotalData.data[reference[key]]) {
     const prop = reference[key]; 
     obj[prop] = myTotalData.data[prop];
   }
   return obj;
}, {});

console.log(resultData);

edited Nov 5, 2020 at 12:15

answered Nov 5, 2020 at 11:59

lissettdm

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2 Comments

sunilsmith Over a year ago

your entries.reduce way of identifying the object is really good but the problem is that I don't have similar object structure or key name. I have updated my question can you try providing a efficient solution @lissettdm

lissettdm Over a year ago

I think, you need a way to map the props, could be something like this {"isNameRequired": "givenName"}, otherwise it is difficult to identify which properties to map.

Lyubomir Vasilev · Accepted Answer · 2020-11-05 21:40:06Z

1

Here is my solution:

You need to change the keys in the object conditionedObject and remove the is- prefix so that they are the same as the keys in myTotalData. This way the check is easier later.

Then it's pretty straight-forward.

let conditionedObject: {[key: string]: boolean} = {
    "isName": true,
    "isCity": false,
    "isPost": true
};

type DataType = {[key: string]: string};
let myTotalData: DataType = {
    "name": 'myname',
    "city": 'mycity',
    "post": 'mypost'
};

let resultData: DataType = {};
for(const key in conditionedObject) {
    // Ensure that the key is really part of this object
    if(!conditionedObject.hasOwnProperty(key)) {
        continue;
    }
    
    if(!conditionedObject[key]) {
        continue;
    }
    
    const dataKey = key.startsWith("is")
        ? key.charAt(2).toLowerCase() + key.substring(3)
        : key;

    if(myTotalData.hasOwnProperty(dataKey)) {
        resultData[dataKey] = myTotalData[dataKey];
    }
}

console.log(resultData);

Output:

{
    name: "myname",
    post: "mypost"
}

edited Nov 5, 2020 at 21:40

answered Nov 5, 2020 at 6:55

Lyubomir Vasilev

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4 Comments

sunilsmith Over a year ago

I cannot have the same keys in both the objects as they both come from different source, is there any other efficient way with the sample objects that I have provided.

Lyubomir Vasilev Over a year ago

Sure. I've updated my answer to use the original conditionedObject.

sunilsmith Over a year ago

not working in TS and got the below error for line if(!conditionedObject[key]) { Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{ isName: boolean; isCity: boolean; isPost: boolean; }'. No index signature with a parameter of type 'string' was found on type '{ isName: boolean; isCity: boolean; isPost: boolean; }'

Lyubomir Vasilev Over a year ago

@sunilsmith That error can be resolved by specifying the types of the data objects, as {[key: string]: boolean} and {[key: string]: strnig}. Updated the answer with the changes, and it no longer has that error.

HynekS · Accepted Answer · 2020-11-05 11:12:02Z

You can use something like that, if you can be sure that the conditionedObject keys are always equal your myTotalData keys, but capitalized and with "is" on the front:

let capitalize = str => str.charAt(0).toUpperCase() + str.slice(1)
let prependIs = str => "is" + str

let conditionedObject = {
  "isName": true,
  "isCity": false,
  "isPost": true
};

let myTotalData = {
  "name": 'myname',
  "city": 'mycity',
  "post": 'mypost'
};

let filterData = (data, conditionObj) => Object.fromEntries(Object.entries(data)
  .filter(([key, _]) => conditionObj[prependIs(capitalize(key))]))

// More verbose alternative for browsers which doesn't support `Object.fromEntries()`
let filterDataAlt = (data, conditionObj) => {
  let result = {}
  let filteredEntries = Object.entries(data)
    .filter(([key, _]) => conditionObj[prependIs(capitalize(key))])
  for (let [key, value] of filteredEntries) {
    result[key] = value
  }
  return result
}

console.log(filterData(myTotalData, conditionedObject))
console.log(filterDataAlt(myTotalData, conditionedObject))

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