Loop through array inside a value JavaScript object

Question

I have a Javascript project in which I am trying to iterate through an Array that is found as a value inside a property, to get the key and from this key get its values from another object.

Right now I can only get the key of the property that contains only one value, I need to get the key of the properties that have arrays as value.

This is the input value:

let asset = "test";

This is the first object I need to get the key that the above value belongs to:

let testData = {
  "data1": ["CAR,PLANE"],
  "data2":["COUNTRY,CITY"],
  "data3":"TEST"
};

This is the second object, from which I have to get the values depending on the previous key:

let dataObj = {
  "data1": [
    "t1Data1",
    "t2Data1",
    "t3Data1"
  ],
  "data2": [
    "t1Data2",
    "t2Data2",
    "t3Data2"
  ],
  "data3": [
    "t1Data3",
    "t2Data3",
    "t3Data3"
  ]
};

This is what I do to get the key:

let res = Object.keys(testData).find(key => testData[key] === asset.toUpperCase());

This is what it returns when the value is a single String:

data3

This is what it returns when the value is inside an array (let asset = "car";):

undefined

This is what I need:

data1

This is what I do to iterate through the array:

for(let getData of testData.data1) {
  console.log(getData)
}

I need to iterate through the array when getting the key, but I don't know how to include this in the res variable.

In testData you may have either a string such as "TEST" or an array such as ["CAR,PLANE"]. The condition for the .find only checks for string to match; and doesn't check for array. — jsN00b
– jsN00b, Commented May 10, 2022 at 15:29
@jsN00b I'm sorry, I don't understand what you mean, what I'm trying to do is go through an array that is as a value inside a property of an object — prueba once
– prueba once, Commented May 10, 2022 at 15:36
testData[key] === asset.toUpperCase() condition is evaluated as truthy when the left-side of === is a string "TEST" and the right-side is another string test (which is stored in variable asset). Now, please think about what happens when right-side is string car (from variable asset), but left-side is ["CAR,PLANE"]. — jsN00b
– jsN00b, Commented May 10, 2022 at 15:54
@jsN00b Ok now I understand, I think I would need to do a forEach on the left side to match the right side, I'm going to try — prueba once
– prueba once, Commented May 10, 2022 at 15:59
One more observation. When checking for the value, using === for "car" will fail because the string contained in the array is "CAR,PLANE". It is one string. So, comparing it for equality (ie, ===) will fail. You may need to split the string "CAR,PLANE" into an array of strings and then use equality on each element. Will try to post an answer. — jsN00b
– jsN00b, Commented May 10, 2022 at 16:02

PeterKA · Accepted Answer · 2022-05-10 16:08:15Z

1

You can convert string values into array, while leaving array values unchanged and then use Array#includes and Array#find methods as follows:

const asset = "test",
      dataObj = {
          "data1": ["CAR","TRUCK","TRAIN"],
          "data2": ["PLANT","TREE","SEEDLING"],
          "data3": "TEST"
      },
      
      output = (o,k) => (Object.entries(o).find(
          ([key,value]) =>
          [].concat(...[value]).includes(k.toUpperCase())
      ) || 
      ['NOT FOUND'])[0];
      
console.log( output(dataObj,asset) );
console.log( output(dataObj,"car") );
console.log( output(dataObj,"skooter") );

answered May 10, 2022 at 16:08

PeterKA

24.7k5 gold badges28 silver badges52 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

nanobar · Accepted Answer · 2022-05-10 16:12:46Z

0

You need to go through each item in the array:

let dataObj = {
  data1: ['t1Data1', 't2Data1', 't3Data1'],
  data2: ['t1Data2', 't2Data2', 't3Data2'],
  data3: ['t1Data3', 't2Data3', 't3Data3'],
};

let testData = {
  data1: ['CAR,PLANE'],
  data2: ['COUNTRY,CITY'],
  data3: 'TEST',
};

let asset = 'car';

let res = Object.keys(testData).find(key => {
  const value = testData[key]

  if (Array.isArray(value)) {
    // Go through each item in the array and compare
    return value.some(item => item.toLowerCase().includes(asset))
  }

  return value.toLowerCase().includes(asset)
})

console.log(res);

answered May 10, 2022 at 16:12

nanobar

66.8k26 gold badges155 silver badges178 bronze badges

Comments

Guillaume · Accepted Answer · 2022-05-10 15:29:28Z

0

Maybe you could try something like this ?

let res = Object.keys(testData).find(key => typeof testData[key] === 'object' ? testData[key].includes(asset.toUpperCase()) : testData[key] === asset.toUpperCase());

answered May 10, 2022 at 15:29

Guillaume

4392 silver badges15 bronze badges

2 Comments

prueba once Over a year ago

This returns an undefined when I pass it some variable that is in an array. What I need is to know how to loop through a String array inside a Javascript object. This is the code I am testing: stackblitz.com/edit/typescript-qe4tsg?file=index.ts

Guillaume Over a year ago

Okay didn't notice the format or your array. use split so : testData[key][0].split(",").includes(asset.toUpperCase())

CER · Accepted Answer · 2022-05-10 16:13:53Z

The value of data1 is ["CAR,PLANE"]. A single element in an array. Your logic assumes "CAR" and "PLANE" are 2 individual string elements of an array. You can change your code to the following (assuming you always have a single element in the array).

let dataObj = {
  data1: ['t1Data1', 't2Data1', 't3Data1'],
  data2: ['t1Data2', 't2Data2', 't3Data2'],
  data3: ['t1Data3', 't2Data3', 't3Data3'],
};

let testData = {
  data1: ['CAR,PLANE'],
  data2: ['COUNTRY,CITY'],
  data3: 'TEST',
};

let asset = 'car';

let res = Object.keys(testData).find((key) =>
  typeof testData[key] === 'object'
    ? testData[key][0].includes(asset.toUpperCase())
    : testData[key] === asset.toUpperCase()
);

console.log(res);

Notice the [0] in ? testData[key][0].includes(asset.toUpperCase()).

If your example is wrong and ["CAR,PLANE"] should really be ["CAR", "PLANE"], I believe your code should work.

jsN00b · Accepted Answer · 2022-05-10 16:16:59Z

Presented below is one possible way to achieve the desired objective.

Code Snippet

// method to find the key
const findKeyFor = (val, obj) => (
  // iterate over key-value pairs of given object 'obj'
  Object.entries(obj)
    // find key-value pair where
    // value matches the "asset"
  .find(([k, v]) => [v].flat().some(
    // [v].flat() accounts for value in "testData"
    // being either string or array of string
    elt => elt.split(',').some(
      // "elt.split()" accounts for string separated
      // by comma such as "CAR,PLANE"
      w => w === val.toUpperCase()
    )
  ))
  ?.[0]                 // extract only the "key"
  ?? 'not found'        // if not found,
);

const testData = {
  "data1": ["CAR,PLANE"],
  "data2":["COUNTRY,CITY"],
  "data3":"TEST"
};

let asset1 = 'test';
let asset2 = 'car';

console.log(
  'find key for "test": ',
  findKeyFor(asset1, testData)
);

console.log(
  'find key for "car": ',
  findKeyFor(asset2, testData)
);

let dataObj = {
  "data1": [
    "t1Data1",
    "t2Data1",
    "t3Data1"
  ],
  "data2": [
    "t1Data2",
    "t2Data2",
    "t3Data2"
  ],
  "data3": [
    "t1Data3",
    "t2Data3",
    "t3Data3"
  ]
};

// to get the value from "dataObj" using the above method
console.log(
  'get dataObj array for "test": ',
  dataObj?.[findKeyFor('test', testData)]
);

console.log(
  'get dataObj array for "car": ',
  dataObj?.[findKeyFor('car', testData)]
);

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

Explanation

Inline comments added to the snippet above.

Collectives™ on Stack Overflow

Loop through array inside a value JavaScript object

5 Answers 5

Comments

Comments

2 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

Comments

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related