How do I loop through Javascript object checking key and values?

Question

I have a Javascript object :

const mapping = {

  'Mind Management': {
    type: 'average',
    linked_topics: ['Digital Detox', 'Small Scaling', 'Simplexity'],
    edge: 'Zeroed Out'
  },

  'Ancient Wisdom': {
    type: 'direct',
    edge: 'Roots Revival'
  }

};

I want to iterate through this object and check if the key or the linked_topics (if present) of the object matches a string value.

const stringToBeMatched = 'Simplexity'

Code that I tried:

for (var key in mapping) {
  if(key === stringToBeMatched || mapping[key].linked_topics.includes(stringToBeMatched) ) {
    console.log(`found ${stringToBeMatched} in ${key}`);
  }
}

I'm getting the following eslint error with this:

ESLint: for..in loops iterate over the entire prototype chain, which is virtually never what you want. Use Object.{keys,values,entries}, and iterate over the resulting array.(no-restricted-syntax)

How can this be fixed? Is there any better way to achieve this without using for..in?

https://stackoverflow.com/questions/684672/how-do-i-loop-through-or-enumerate-a-javascript-object — shushu304, Dec 23 '21 at 11:31
what result do you expect? the outer ptoperty name or the index of the array or both? — Nina Scholz, Dec 23 '21 at 11:32

score 1 · Answer 1 · answered Dec 23 '21 at 11:31

You can get only the keys using Object.keys

const keys = Object.keys(mapping);

keys.forEach((key) => {
  if(key === stringToBeMatched || mapping[key].linked_topics.includes(stringToBeMatched) ) {
    console.log(`found ${stringToBeMatched} in ${key}`);
  }
})

score 1 · Answer 2 · answered Dec 23 '21 at 11:35

Use entries as suggested by ESLint. I used ?. instead of . after "linked_topics" property to prevent Cannot read properties of undefined (reading 'includes') error when no property exists named linked_topics.

const stringToBeMatched = 'Simplexity' 

Object.entries(mapping).forEach(([key, value]) => {
  if(key === stringToBeMatched || value.linked_topics?.includes(stringToBeMatched) ) {
    console.log(`found ${stringToBeMatched} in ${key}`);
  }
})

score 1 · Accepted Answer · answered Dec 23 '21 at 11:46

Good answer from @doctorgu, you could also you some.

const string = 'Simplexity'

const mapping = {
  'Mind Management': {
    type: 'average',
    linked_topics: ['Digital Detox', 'Small Scaling', 'Simplexity'],
    edge: 'Zeroed Out'
  },
  'Ancient Wisdom': {
    type: 'direct',
    edge: 'Roots Revival'
  }
}

const isStringInMapping = Object.entries(mapping).some(([key, value]) => (
    key == string || value.linked_topics?.includes(string)
))

console.log(isStringInMapping)

How do I loop through Javascript object checking key and values?

3 Answers3