3 Ways to Build Query Strings In Javascript (Simple Examples)

Welcome to a quick tutorial and examples on how to build a query string in Javascript. So you want to send data from one place to another and need to create a URL string with parameters?

That covers the basics, but there are more methods that we can use – Read on for more!

 

 

TLDR – QUICK SLIDES

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TABLE OF CONTENTS

 

 

 

METHOD 1) URL PARAMS OBJECT

<script>
// (A) URL SEARCH PARAMS OBJECT TO QUICKLY BUILD QUERY STRING
var query = new URLSearchParams({
  name : "Jon Doe", 
  email : "jon@doe.com",
  colors : JSON.stringify(["Red", "Green", "Blue"])
});
query.append("KEY", "VALUE"); // to append more data
 
// (B) CONVERT TO STRING, APPEND TO URL
var url = "http://site.com/page?" + query.toString();
console.log(url);
 
// (C) WHATEVER COMES NEXT
// window.location.href = url;
// fetch(url).then(res=>res.text()).then(txt=>console.log(txt));
</script>

As in the introduction above, this is one of the easiest ways to build a query string in modern-day Javascript – Just create a new URLSearchParams() object, append data, and convert it toString() – Done.

 

 

METHOD 2) USING URI.JS LIBRARY

<!-- CHECK https://cdnjs.com/libraries/URI.js FOR LATEST VERSION -->
<!-- DOCS: https://medialize.github.io/URI.js/ -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/URI.js/1.19.11/URI.min.js"></script>
<script>
// (A) TARGET URL
var uri = new URI("http://site.com/page");
 
// (B) SET PARAMETERS
uri.setSearch({
  name : "Jon Doe",
  email : "jon@doe.com",
  colors : JSON.stringify(["Red", "Green", "Blue"])
});
uri.addSearch("KEY", "VALUE"); // to append more data
 
// (C) OUTPUT ENTIRE URL STRING
var url = uri.toString();
console.log(url);
 
// (D) WHATEVER COMES NEXT
// window.location.href = url;
// fetch(url).then(res=>res.text()).then(txt=>console.log(txt));
</script>

Now, URLSearchParams is well-supported in most modern browsers. But when you have to work with ancient browsers, this is a possible alternative – Use a library called URI.JS. The syntax is pretty much the same and should be straightforward enough. Check out the official URI.js documentation if you want to learn more about this library.

 

 

METHOD 3) MANUAL QUERY STRING

<script>
// (A) TARGET URL
var url = encodeURI("http://site.com/mypage");
 
// (B) APPEND DATA TO QUERY STRING
// TAKE NOTE - ?KEY FOR FIRST PARAMETER, &KEY FOR MORE PARAMETERS
url += "?name=" + encodeURIComponent("Jon Doe");
url += "&email=" + encodeURIComponent("jon@doe.com");
url += "&KEY=" + encodeURIComponent("VALUE");
 
// (C) TO APPEND AN ARRAY - JSON ENCODE
var colors = ["Red", "Green", "Blue"];
url += "&colors=" + JSON.stringify(colors);
 
// (D) FULL URL
// http://site.com/my%20page?name=John%20Doe&email=john%40doe.com&KEY=VALUE&colors=["Red","Green","Blue"]
console.log(url);
 
// (E) WHATEVER COMES NEXT
// window.location.href = url;
// fetch(url).then(res=>res.text()).then(txt=>console.log(txt));
</script>

When all else fails, this is the traditional way to create a query string – Manually. Just take a moment to understand the syntax:

• Query strings are appended to the end of the URL – http://site.com/page?KEY=VALUE&KEY=VALUE...
• Take note of the use of encodeURI() and encodeURIComponent() here.
  • Some characters such as empty spaces and @ are not allowed in the URL. These functions will convert these “illegal characters” to their respective code.
  • The rather confusing part is that we have to use encodeURI() for the http://site.com/path/ part, and encodeURIComponenet() for the parameters.
  • Basically, some history here – The URL and parameter both accept rather different character sets… Just take note, to use different encode functions for each segment.

 

 

 

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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.

 

 

LINKS & REFERENCES

• How to build query string with Javascript – Stack Overflow
• Easiest way to get and create url search params: Javascript – ITNext
• Arrays in query params – Jonathan Stoikovitch

 

USEFUL FUNCTIONS & OBJECTS TO KNOW

Function/Object	Description	Reference Link
encodeURI()	Encode the URL.	Click Here
encodeURIComponent()	Encode a single URI component.	Click Here
new URLSearchParams()	URL parameters object.	Click Here

 

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