fetch API returning an empty string

Question

I am trying to get a page's HTML using fetch API. Here is my code.

var quizUrl = 'http://www.lipsum.com/';
var myHeaders = new Headers();
myHeaders.append('Content-Type', 'text/html');
fetch(quizUrl,{
    mode: 'no-cors',
    method: 'get',
    headers: myHeaders
}).then(function(response) {
    response.text().then(function(text) {
        console.log(text);
    })
}).catch(function(err) {
  console.log(err)
});

It returns empty string. Any guesses why it doesn't work?

Solution 1

About the Request.mode'no-cors' _{(from MDN, emphasis mine)}

Prevents the method from being anything other than HEAD, GET or POST. If any ServiceWorkers intercept these requests, they may not add or override any headers except for these. In addition, JavaScript may not access any properties of the resulting Response. This ensures that ServiceWorkers do not affect the semantics of the Web and prevents security and privacy issues arising from leaking data across domains.

So this will enable the request, but will make the Response as opaque, i.e, you won't be able to get anything from it, except knowing that the target is there.

Since you are trying to fetch a cross-origin domain, nothing much to do than a proxy routing.

---

PS : here is a snippet showing you that the request is indeed opaque :

var quizUrl = 'http://www.lipsum.com/';
fetch(quizUrl, {
  mode: 'no-cors',
  method: 'get'
}).then(function(response) {
  console.log(response.type)
}).catch(function(err) {
  console.log(err) // this won't trigger because there is no actual error
});

Solution 2

I guess this might help, use as below:

fetch('/url/to/server')
.then(res => {
    return res.text();
})
.then(data => {
    $('#container').html(data);
});

And in server side, return content as plain text without setting header content-type.

I used $('#container') to represent the container that you want the html data to go after retrieving it.

The difference with fetching json data is using res.json() in place of res.text() And also, don't append any headers

Solution 3

2021 answer: just in case you land here looking for how to make GET and POST Fetch api requests using async/await or promises as compared to axios.

I'm using jsonplaceholder fake API to demonstrate:

Fetch api GET request using async/await:

         const asyncGetCall = async () => {
            try {
                const response = await fetch('https://jsonplaceholder.typicode.com/posts');
                 const data = await response.json();
                // enter you logic when the fetch is successful
                 console.log(data);
               } catch(error) {
            // enter your logic for when there is an error (ex. error toast)
                  console.log(error)
                 } 
            }
          asyncGetCall()

Fetch api POST request using async/await:

    const asyncPostCall = async () => {
            try {
                const response = await fetch('https://jsonplaceholder.typicode.com/posts', {
                 method: 'POST',
                 headers: {
                   'Content-Type': 'application/json'
                   },
                   body: JSON.stringify({
             // your expected POST request payload goes here
                     title: "My post title",
                     body: "My post content."
                    })
                 });
                 const data = await response.json();
              // enter you logic when the fetch is successful
                 console.log(data);
               } catch(error) {
             // enter your logic for when there is an error (ex. error toast)
                  console.log(error)
                 } 
            }
asyncPostCall()

GET request using Promises:

  fetch('https://jsonplaceholder.typicode.com/posts')
  .then(res => res.json())
  .then(data => {
   // enter you logic when the fetch is successful
    console.log(data)
  })
  .catch(error => {
    // enter your logic for when there is an error (ex. error toast)
   console.log(error)
  })

POST request using Promises:

fetch('https://jsonplaceholder.typicode.com/posts', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
  },
   body: JSON.stringify({
     // your expected POST request payload goes here
      title: "My post title",
      body: "My post content."
      })
})
  .then(res => res.json())
  .then(data => {
   // enter you logic when the fetch is successful
    console.log(data)
  })
  .catch(error => {
  // enter your logic for when there is an error (ex. error toast)
   console.log(error)
  })  

GET request using Axios:

        const axiosGetCall = async () => {
            try {
              const { data } = await axios.get('https://jsonplaceholder.typicode.com/posts')
    // enter you logic when the fetch is successful
              console.log(`data: `, data)
            } catch (error) {
    // enter your logic for when there is an error (ex. error toast)
              console.log(`error: `, error)
            }
          }
    axiosGetCall()

POST request using Axios:

const axiosPostCall = async () => {
    try {
      const { data } = await axios.post('https://jsonplaceholder.typicode.com/posts',  {
      // your expected POST request payload goes here
      title: "My post title",
      body: "My post content."
      })
   // enter you logic when the fetch is successful
      console.log(`data: `, data)
    } catch (error) {
  // enter your logic for when there is an error (ex. error toast)
      console.log(`error: `, error)
    }
  }
axiosPostCall()