Utilizing Regular Expressions to Substitute 'null' in API Data with a Custom String in JavaScript

Question

Utilizing Regular Expressions to Substitute 'null' in API Data with a Custom String in JavaScript

I'm working with an API to gather information about books, including the title and author. However, I've noticed that some authors' data is returned as 'undefined'. I had the idea of using regular expressions (RegExp) to replace this undefined value with 'N/A', but I am encountering difficulties implementing it.

/* within a function */
function fetchingAsyncData() {

  /* data fetching process */

  const responseData = await response.json();

  const foundBooks = [];

  for (let i = 0; i < responseData.items.length; i++) {
    let bookTitle = responseData.items[i].title;
    let bookAuthor = responseData.items[i].author;

    if (typeof bookTitle === 'undefined' || typeof bookAuthor === 'undefined') {

      // Attempting to replace 'undefined' with 'N/A'

    }

    foundBooks.push(`${responseData.items[i].title} by ${responseData.items[i].authors}`);
  }

  return foundBooks;
}

An example of the current output: ["Cats by undefined"], however I am aiming for the desired result: ["Cats by N/A"].

javascript json regex

Answer 1

Answer №1

There is no need to use a regular expression in this situation, as undefined is not a string but a special type. The best approach is to simply replace the value with a default option; a common method is to use short-circuiting:

let titles = data.items[i].title || 'N/A';
let authors = data.items[i].author || 'N/A';

This technique works because the || ("or") operator chooses the first non-falsy value from the list, or the last one if they are all falsy. Since undefined is considered falsy and strings are truthy, this code snippet will assign the existing string value if it is present, or 'N/A' if it is undefined.

Answer 2

There is no need to use a regular expression in this situation, as undefined is not a string but a special type. The best approach is to simply replace the value with a default option; a common method is to use short-circuiting:

let titles = data.items[i].title || 'N/A';
let authors = data.items[i].author || 'N/A';

This technique works because the || ("or") operator chooses the first non-falsy value from the list, or the last one if they are all falsy. Since undefined is considered falsy and strings are truthy, this code snippet will assign the existing string value if it is present, or 'N/A' if it is undefined.

Answer 3

Answer №2

This method presents a unique approach by utilizing a default object to fill in any missing gaps within the objects provided. The main benefit is that it simplifies the process of adding new properties during consolidation, making it more manageable. However, it is important to note that this approach does not leave much room for inherent logic when filling in these gaps.

const def = {author: 'N/A', title: 'N/A'} 
let data = [
  { author: 'A1', title: 'T1'},
  { author: 'A2'},
  { title: 'T2'}
]

data = data.map(x => Object.assign({},def , x))

console.log(data)

Answer 4

This method presents a unique approach by utilizing a default object to fill in any missing gaps within the objects provided. The main benefit is that it simplifies the process of adding new properties during consolidation, making it more manageable. However, it is important to note that this approach does not leave much room for inherent logic when filling in these gaps.

const def = {author: 'N/A', title: 'N/A'} 
let data = [
  { author: 'A1', title: 'T1'},
  { author: 'A2'},
  { title: 'T2'}
]

data = data.map(x => Object.assign({},def , x))

console.log(data)

Answer 5

Answer №3

If the variable titles is of type string and contains the value "undefined", you can manipulate it using RegEx with following code:

...
titles = titles.replace(/undefined/g, "N/A");
...

However, if titles is actually undefined (has no value), it's recommended to handle it like this:

titles = titles || 'N/A';

This will set titles to "N/A" if it's undefined, null, empty string or 0 (for number type), otherwise it will keep the original value of titles.

Answer 6

If the variable titles is of type string and contains the value "undefined", you can manipulate it using RegEx with following code:

...
titles = titles.replace(/undefined/g, "N/A");
...

However, if titles is actually undefined (has no value), it's recommended to handle it like this:

titles = titles || 'N/A';

This will set titles to "N/A" if it's undefined, null, empty string or 0 (for number type), otherwise it will keep the original value of titles.

Utilizing Regular Expressions to Substitute 'null' in API Data with a Custom String in JavaScript

Answer №1

Answer №2

Answer №3

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