Javascript loop not returning true, when String === String

Question

When looping through an array to find if the array contains a word that I am looking for, the loop always returns 'false' when if I console.log out the what is being compared I can clearly see that the word I am looking for (collectionNameLookingFor) is in the array (collectionNameArray) so it should return true.

function checkCollectionNames(arrayOfCollections, collectionName) {
  for (let i = 0; i < arrayofCollections.length; i++) {
    if (arrayOfCollections[i] === collectionName) {
      return true;
    }
  }
  return false;
}

function saveContentToDb(req, res) {
  const db = getDb();
  const pageDetails = req.body;
  let saveType;

  db.db(pageDetails.databaseName).listCollections().toArray((error, collections) => {
    if (error) {
      throw error;
    } else {
      collections.map(collection => (collection.name)).forEach(collectionNameArray => {
        const collectionNameLookingFor = req.body.page;
        const check = checkCollectionNames(collectionNameArray, collectionNameLookingFor);

        console.log('===========Looking to see if it is true or false==========');
        console.log(check);
        console.log(`Name of collection in Database: ${collectionNameArray} ::: ${collectionNameLookingFor}`);
        console.log('==========================================================');
        if (check === true) {
          saveType = 'updated';
          console.log(`saveType = ${saveType}`);
        } else {
          saveType = 'created';
          console.log(`saveType = ${saveType}`);
        }
      });
    }
  });
}

checkCollectionNames has a first parameter called arrayOfCollections, but you refer to it in the function itself as simply array. Surely these should match? — Robin Zigmond
– Robin Zigmond, Commented Mar 13, 2019 at 14:14
Have you considered using the Array.prototype.includes method instead of writing your own? — Randy Casburn
– Randy Casburn, Commented Mar 13, 2019 at 14:15
Can you please check that the elements of the array are string or object. use "console.log(typeof array[i])". Because you can create string in form of object using new String(...). — RK_15
– RK_15, Commented Mar 13, 2019 at 14:18
If the array elements are objects then use of "==" instead of "===" will do the work. — RK_15
– RK_15, Commented Mar 13, 2019 at 14:21

Emma Marcier · Accepted Answer · 2019-03-13 19:41:34Z

0

You might need to check against collectionName, because that is the parameter you hand over, beside arrayOfCollections, instead of the array itself.

function checkCollectionNames(arrayOfCollections, collectionName) {
    for (let i = 0; i < arrayOfCollections.length; i++) {
        if (arrayOfCollections[i] === collectionName) {
            return true;
        }
    }
    return false;
}

Short Version:

function checkCollectionNames(arrayOfCollections, collectionName) {
    return arrayOfCollections.includes(collectionName);
}

edited Mar 13, 2019 at 19:41

Emma Marcier

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answered Mar 13, 2019 at 14:15

Nina Scholz

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3 Comments

Andrew Over a year ago

That was a mistake when copy over to into the question. I've edited the question to fix this.

Andrew Over a year ago

When logging out there are 5 values in the array, and the one that matches does return true, e.g. saveType = 'updated'. But the once it returns true it doesn't break, so the loop keeps going and ends up returning false, e.g. saveType = 'created' because the final value is False.

Nina Scholz Over a year ago

are you sure, that the collection contains strings and the wanted value is a string, too?

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