Javascript Fetch With GET Query Params (Quick Examples)

Welcome to a tutorial and example on how to send a Javascript fetch request with GET query parameters. New to the fetch API, and trying to pass in some query parameters?

That covers the quick basics, but read on for detailed examples.

 

 

TLDR – QUICK SLIDES

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TABLE OF CONTENTS

 

 

 

EXAMPLE 1) APPEND SEARCH PARAMS

<script>
function fetchGet () {
  // (A) DATA TO SEND
  var data = {
    name : "jon doe",
    email : "jon@doe.com"
  };
 
  // (B) BUILD URL
  var url = new URL("http://site.com/0-dummy.php");
  for (let k in data) { url.searchParams.append(k, data[k]); }
  console.log(url);
 
  // (C) FETCH WITH GET SEARCH PARAMS
  fetch(url)
 
  // (D) RETURN SERVER RESPONSE AS TEXT
  .then(res => {
    console.log(res);
    if (res.status != 200) { throw new Error("Bad Server Response"); }
    return res.text();
  })
  .then(res => console.log(res))
 
  // (E) HANDLE ERRORS (OPTIONAL)
  .catch(err => console.error(err));
}
</script>
 
<input type="button" value="Fetch Get" onclick="fetchGet()">

This is the “full version” of the introduction snippet. As you can see, the parameters are attached to the URL itself, it has nothing much to do with fetch(). Take note of how we generate the URL though:

• var url = new URL();
• url.searchParams.append(KEY, VALUE);

The URL search params API is well-supported in all modern browsers at the time of writing, but take note that it will not work on the old Internet Exploders (caniuse.com).

 

 

EXAMPLE 2) MANUAL URL ENCODE

<script>
function fetchGet () {
  // (A) DATA TO SEND
  var data = {
    name : "jon doe",
    email : "jon@doe.com"
  };
 
  // (B) MANUAL CONSTRUCT URL & PARAMS
  var url = "http://site.com/0-dummy.php";
  url += "?";
  for (let k in data) { url += k + "=" + data[k] + "&"; }
  url = encodeURI(url.slice(0, -1));
 
  // (C) FETCH WITH GET SEARCH PARAMS
  fetch(url)
 
  // (D) RETURN SERVER RESPONSE AS TEXT
  .then(res => {
    console.log(res);
    if (res.status != 200) { throw new Error("Bad Server Response"); }
    return res.text();
  })
  .then(res => console.log(response))
 
  // (E) HANDLE ERRORS (OPTIONAL)
  .catch(err => console.error(err));
}
</script>
 
<input type="button" value="Fetch Get" onclick="fetchGet()">

If you have to support older browsers, the only way is to manually construct the URL string and parameters.

• Simply append the parameters behind the URL – http://site.com/path?KEY=VALUE&KEY=VALUE
• Then encode the URL using encodeURI().

 

 

 

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EXAMPLE CODE DOWNLOAD

Click here for the source code on GitHub gist, just click on “download zip” or do a git clone. I have released it under the MIT license, so feel free to build on top of it or use it in your own project.

 

 

COMPATIBILITY CHECKS

• Arrow Functions – CanIUse
• Fetch API – CanIUse
• URL Search Params – CanIUse

The examples will work on all modern browsers. Old Internet Exploders, beware.

 

LINKS & REFERENCES

• Fetch API – MDN
• POST Form Data With Fetch – Code Boxx

 

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