Comparing strings in arrays using JavaScript

Question

Comparing strings in arrays using JavaScript

Currently, I am engrossed in a firebase project involving vuejs. My goal is to create a chart that visually represents the number of subscribers per month. The tricky part lies in accurately calculating the number of user profiles created each month. As for the remaining steps, I feel confident in handling them.

My initial approach involves the following:

// Calculating the number of users each month
let months = ['jan', 'feb', 'mar', 'apr', 'may', 'Jun', 'jul', 'aug', 'sep', 'oct', 'nov', 'dec'];

this.users.filter(user => {
  let print = user.metadata.creationTime;

  for (var month in months) {
    if (print.indexOf(month) > -1) {
      console.log(user.email)
    }
  }
})

As I tested this solution, I noticed that the console output displayed duplicate records for each month.

Considering this situation, I am pondering whether there exists an alternative method to achieve the desired outcome, or should I persist with refining and experimenting with the current approach?

javascript firebase vue.js vuejs2

Answer 1

Answer №1

It seems like you're aiming for a structure similar to this:

// Example data
const users = [
  { metadata: { creationTime: '3 apr' } },
  { metadata: { creationTime: '7 apr' } },
  { metadata: { creationTime: '26 jan' } },
  { metadata: { creationTime: '4 feb' } },
  { metadata: { creationTime: '9 dec' } },
  { metadata: { creationTime: '25 dec' } },
  { metadata: { creationTime: '9 apr' } }
]

// Lower-case month names... assuming creationTime is also in lower-case
const months = ['jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul', 'aug', 'sep', 'oct', 'nov', 'dec']

// Using `map` to create an array with counts for each month
const counts = months.map(month => {
  let count = 0
  
  // Looping through the `users` array using `of` instead of `in`
  for (const user of users) {
    // Using `includes` to check for month in creationTime
    if (user.metadata.creationTime.includes(month)) {
      ++count
    }
  }
  
  return count
})

console.log('Counts: ' + counts.join(' '))

In this case, the output is an array with counts for each month. You can modify the return value in the map function to return objects with month names and counts if that suits your needs better.

Your original code had a flaw with for (var month in months) {. This loop iterates over numeric indices instead of month names, resulting in checking for 0, 1, 2, etc. rather than jan, feb, mar, etc.. To iterate over the array contents, consider using a for/of loop instead.

Answer 2

It seems like you're aiming for a structure similar to this:

// Example data
const users = [
  { metadata: { creationTime: '3 apr' } },
  { metadata: { creationTime: '7 apr' } },
  { metadata: { creationTime: '26 jan' } },
  { metadata: { creationTime: '4 feb' } },
  { metadata: { creationTime: '9 dec' } },
  { metadata: { creationTime: '25 dec' } },
  { metadata: { creationTime: '9 apr' } }
]

// Lower-case month names... assuming creationTime is also in lower-case
const months = ['jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul', 'aug', 'sep', 'oct', 'nov', 'dec']

// Using `map` to create an array with counts for each month
const counts = months.map(month => {
  let count = 0
  
  // Looping through the `users` array using `of` instead of `in`
  for (const user of users) {
    // Using `includes` to check for month in creationTime
    if (user.metadata.creationTime.includes(month)) {
      ++count
    }
  }
  
  return count
})

console.log('Counts: ' + counts.join(' '))

In this case, the output is an array with counts for each month. You can modify the return value in the map function to return objects with month names and counts if that suits your needs better.

Your original code had a flaw with for (var month in months) {. This loop iterates over numeric indices instead of month names, resulting in checking for 0, 1, 2, etc. rather than jan, feb, mar, etc.. To iterate over the array contents, consider using a for/of loop instead.

Comparing strings in arrays using JavaScript

Answer №1

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