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JavaScript Create a Reusable Fetch Function

Refactoring generates: app.js:10 Uncaught (in promise) TypeError: res.join is not a function at app.js:10 -

Refactoring to use fetchData generates the above issue:

Used different naming but I fail to find the issue. When taking out the refactoring and adding back the old then(response...) everything is fine.

const select = document.getElementById("breeds");
const card = document.querySelector(".card");
const form = document.querySelector("form");

// ------------------------------------------
// ------------------------------------------
function fetchData(url) {
  return fetch(url)
    .then(res => res.join());

fetchData("https://dog.ceo/api/breeds/list").then((data) =>

function generateListItems(data) {
  const items = data
      (item) => `
      <option value='${item}'>${item}</option>
  select.innerHTML = items;

fetchData("https://dog.ceo/api/breeds/image/random").then((data) =>

function generateImage(data) {
  const html = `
    <img src=${data} alt>
    <p>Click to view image of ${select.value}</p>
  card.innerHTML = html;

function fetchBreedImage() {
  const breed = select.value;
  const img = card.querySelector("img");
  const p = card.querySelector("p");

  fetchData(`https://dog.ceo/api/breed/${breed}/images/random`).then((data) => {
    img.src = data.message;
    img.alt = "breed";
    p.textContent = `Click to view more ${breed}s`

select.addEventListener('change', fetchBreedImage)
card.addEventListener('click', fetchBreedImage)

2 Answers

Blake Larson
Blake Larson
13,014 Points

You want to use the .json() function on the response object, which extracts the JSON body content from the response.

function fetchData(url){
    return fetch(url)
        .then(res => res.json())

I missed the error, thanks a lot!