When to use javascript map vs filter?

filter vs. map

• filter: This method creates a new array with all elements that pass the test implemented by the provided function. It is used when you need to remove elements from an array based on a condition.

• map: This method creates a new array populated with the results of calling a provided function on every element in the calling array. It is used when you need to transform or modify each element of an array.
  
  

  Example 1: Using filter

  const numbers = [1, 2, 3, 4, 5, 6];
  
  // Filter out odd numbers
  const evenNumbers = numbers.filter(num => num % 2 === 0);
  
  console.log(evenNumbers); // Output: [2, 4, 6]
  

  
  Example 2: Using map
  

  const temperaturesCelsius = [0, 20, 30, 40];
  
  // Convert Celsius to Fahrenheit
  const temperaturesFahrenheit = temperaturesCelsius.map(celsius => celsius * 9/5 + 32);
  
  console.log(temperaturesFahrenheit); // Output: [32, 68, 86, 104]

  
  

  Best Practices and Performance Considerations

  1. Use the Right Method for the Job:

     • Choose filter if you need to narrow down the elements based on a condition.
     • Choose map if you need to modify each element of the array.

  2. Avoid Chaining Unnecessary Operations:

     • If you only need to transform elements, use map. Adding a filter after map might indicate a logical error or inefficiency.

  3. Performance Considerations:

     • Both filter and map have linear time complexity (O(n)), so their performance is generally acceptable for most use cases. However, be cautious with very large arrays and multiple chained operations, as they can lead to performance issues.