Скачать или смотреть How to Create a Query String in a URL for Your Links

Learn how to properly create a query string in a URL for a link using JavaScript and avoid common mistakes like undefined parameters.
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This video is based on the question https://stackoverflow.com/q/63717769/ asked by the user 'Pauline Momot' ( https://stackoverflow.com/u/14212964/ ) and on the answer https://stackoverflow.com/a/63717908/ provided by the user 'mplungjan' ( https://stackoverflow.com/u/295783/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Creating a Query String in a URL for Links

In web development, creating dynamic links is a common task. Often, these links need to include query strings to pass data or parameters to another page or script. If you've ever tried to build a URL with a query string in JavaScript only to encounter an issue like receiving an "undefined" value, then this guide is for you!

The Problem: Undefined Parameters

When attempting to append query parameters to a URL with JavaScript, you might be faced with the frustrating situation of getting an "undefined" value for your variables. This can occur due to a few common pitfalls, which we will explore and rectify.

Example Scenario

Let's say you have an array of cameras, from which you want to extract an ID and construct a URL. The following code snippet exemplifies the issue many developers face:

[[See Video to Reveal this Text or Code Snippet]]

In the snippet above, you might notice that the expected output is not achieved. The urlCameras variable is likely returning undefined, which is frustrating when all you want is a correctly formatted URL.

The Solution: Properly Building the Query String

To create a valid query string, there are a few corrections we can make to the code snippet above. Here's a breakdown of the key steps and corrections:

1. Use the append Method Correctly

Instead of trying to append parameters with question mark (?) and equals sign (=) in the append() method, simply provide the parameter name and its value as follows:

Change:

[[See Video to Reveal this Text or Code Snippet]]

To:

[[See Video to Reveal this Text or Code Snippet]]

Important Points:

No need for ? or =: The URLSearchParams object takes care of that for you, so you only need to pass the key and the value.

Avoid quoting variable names: Ensure that you are passing the variable directly instead of as a string. In this case, idCameras should be passed without quotes.

2. Reducing unnecessary variables

You might notice that the code contains redundancy with the params variable. Instead of creating a separate params variable, you can directly use urlObj.searchParams.

Final Code Example

Here's the corrected and streamlined version of your original snippet:

[[See Video to Reveal this Text or Code Snippet]]

HTML Snippet For the Link

In order to create a clickable link that utilizes this script, you can use the following HTML code:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following these simple fixes and understanding how to utilize the URLSearchParams correctly, you can effectively build query strings in JavaScript, ensuring your URLs function correctly and carry the necessary data. Remember, troubleshooting coding issues often involves revisiting the basics and making sure each part works seamlessly together. Happy coding!