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JavaScript JavaScript Array Iteration Methods Array Manipulation Transform Array Items with map()

if map() the same as join()?

why does map and join look the same use?

2 Answers

Bella Bradbury
.a{fill-rule:evenodd;}techdegree seal-36
Bella Bradbury
Front End Web Development Techdegree Graduate 32,790 Points

Hi Peter!

These might look the same upon first glance, but they're actually quite different. Let's break them both down and then compare them with an example!

The join() method creates a concatenated string from an array. This means that it takes all of the separate elements of an array and combines them into just one string. The information is no longer separated. Here's a link to join() documentation.

The map() method creates a new array based off of a different array. This means that the information is still separate and should be transformed in some way. Here's a link to map() documentation.

Let's use an example to really highlight the differences!

let initialArray = [50, 30, 900, 60, 80];

function joinArray() {
  let stringArray = initialArray.join();
  // console will log "50, 30, 900, 60, 80" as a STRING
    // this is one value and not actually separate numbers

function mapArray() {
  let newArray = initialArray.map(x => x / 10);
  // console will log [5, 3, 90, 6, 8] an an ARRAY
    // these are still separate values and is still iterable 

Hopefully this helps with the difference!

Thank you so much!!!