How to write code to understand it?

JavaScript
1 
function findPostById(postId, posts) {
  return posts.find((post) => post.postId === postId)
}

const posts = [
  { postId: 1355, commentsQuantity: 5 },
  { postId: 5131, commentsQuantity: 13 },
  { postId: 6134, commentsQuantity: 2 },
]

console.log(findPostById(6134, posts)) // { postId: 6134, commentsQuantity: 2 }

console.log(findPostById(4511, posts)) // undefined

As always, I don’t understand this form of writing code, who can rewrite the code to make it clear, for example, I don’t understand this line

return posts.find((post) => post.postId === postId)
2

Let’s try this to start with…

let output = [];
posts.forEach((post) => { 
   if (post.postID === postSearchID) { 
     output.push(post); 
   } 
});
return output;

EDIT: Actually it’s dumbfire searching a single entry, so it’s ACTUALLY…

posts.forEach((post) => { 
   if (post.postID === postSearchID) { 
     return post; 
   } 
});
return undefined;
3

Does this help?

function findPostById(postId, posts) {
  const foundPost = posts.find(function(post) {
    if (post.postId === postId) {
      return true;
    }
  });

  return foundPost;
}
4

Or if written with a loop.

function findPostById(postId, posts) {

  // loop through all posts
  for (let i = 0; i < posts.length; i+=1) {

    // do we have a matched postId?
    if (posts[i] === postId) {
      return posts[i] // yes, stop immediately and return that id
    }
  }

  // we have finished the loop without finding a matched postId
  // so return undefined
  return undefined // not really necessary as this will be returned anyway
}

Here are the MDN Docs for Array.find

I don’t know if this confuses things, but elaborating on the above loop, this is basically how Array.find works

// This is what Array.find is doing
function find(arr, callback) {

  // loop through the given array
  for (let i = 0; i < arr.length; i+=1) {

    // pass in each item to the given function
    // and test to see if the function returns true
    if (callback(arr[i])) === true) {
      return arr[i] // true, so return item
    }
  }

  // no matches to 'true'
  return undefined
}


// example using find
function findPostById(posts, postId) {
  
  const foundId = find(
    // the array of posts.
    posts,
    // this is the function to be called on each post.
    function (post) {
      if (post.postId === postId) return true
    }
  )

  return foundId
}
5

For some reason, in every code there is an entry where I do not understand how it works, for example, return foundPost; why doesn’t the code work without it? if the block contains true, then it should output true, but without undefined, and here the error appears immediately

6

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