Скачать или смотреть How to Pass a Script Function to Another HTML Script Page using Local Storage

Discover a simple method to `store and retrieve functions` in JavaScript using local storage, ensuring seamless functionality across multiple HTML pages.
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This video is based on the question https://stackoverflow.com/q/64050864/ asked by the user 'Bernardo Olisan' ( https://stackoverflow.com/u/12586440/ ) and on the answer https://stackoverflow.com/a/64050996/ provided by the user 'ΔO 'delta zero'' ( https://stackoverflow.com/u/3290062/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

Have you ever found yourself needing to pass a script function from one HTML page to another? This common scenario can arise when you want to maintain functionality across different pages in your web application. In this guide, we will explore how to work around limitations by utilizing local storage to store JavaScript functions and then retrieve and execute them on a separate page.

Understanding the Problem

When you want a JavaScript function to be accessible across multiple pages, you might think about storing it directly using local storage. However, it's essential to note that local storage does not support storing functions directly. If you try to store a function, you'll likely end up storing just the return value of that function instead of the function itself.

Example: The Payment Function

For clarity, let's begin with a sample function:

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

Here, the Payment function is designed to greet the user by their name, obtained from an input field. If you attempted to store it like this:

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

You would encounter a problem, as this only stores the result of calling the Payment function, not the function itself.

The Solution: Storing and Retrieving Functions

Instead of trying to store the function directly, we can convert it to a string representation that can later be evaluated back into a function. Here’s the step-by-step approach.

Step 1: Store the Function as a String

Instead of calling the function and storing its return value, we'll store the function's string version:

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

Step 2: Retrieving and Evaluating the Function

Later, when you need to use the Payment function, you can retrieve it from local storage and convert it back into a callable function using eval(). Here's how you can do that:

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

Important Considerations

Security: Using eval() can introduce significant security risks, especially if any user-generated content can be evaluated. Ensure that you have full control over the code being evaluated or explore safer alternatives, such as predefining functions on your pages.

Browser Compatibility: Most modern browsers support local storage, but always verify compatibility if you're targeting a broad audience.

Performance: Storing large amounts of code can affect performance. Use local storage judiciously.

Conclusion

Passing script functions between HTML pages can initially seem daunting due to the limitations of local storage. However, by converting the function into a string representation and utilizing eval(), you can successfully store and later retrieve and execute JavaScript functions. This method empowers your web applications with increased modularity and functionality across different pages.

Feel free to experiment with the examples provided, and reach out if you have any questions or run into issues. Happy coding!