Скачать или смотреть How to Generate Indefinite Number of Charts in JavaScript Using Chart.js

Learn how to dynamically create and retrieve multiple charts using Chart.js while managing canvas objects efficiently.
---
This video is based on the question https://stackoverflow.com/q/70000635/ asked by the user 'Thomas Zlabinger' ( https://stackoverflow.com/u/10406795/ ) and on the answer https://stackoverflow.com/a/70032235/ provided by the user 'Thomas Zlabinger' ( https://stackoverflow.com/u/10406795/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Generate an indefinite number of charts as images (chart.js)

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Generating Indefinite Numbers of Charts with Chart.js

Are you looking for a way to dynamically generate multiple line charts as image files from data fetched from a database? If so, we have the perfect solution for you. In this guide, we will guide you through the process of creating an indefinite number of charts using Chart.js, focusing on potential pitfalls and how to resolve them.

The Problem

When attempting to create multiple line charts from separate data points queried from a database, users often encounter issues such as:

The same output being returned every time for the image file created, regardless of the data passed to the function.

Only the last dataset queried being returned when inspecting the data inside animation callbacks.

This can be frustrating, but with the right approach, you can solve these issues effectively.

Understanding the Solution

The key to resolving the problems lies in creating a separate canvas object for each chart. In doing so, you ensure that each line chart retains its unique dataset, allowing you to generate distinct images as needed.

Steps to Implement the Solution

Create a Canvas Object Dynamically:
Before you call the function to create your chart, dynamically generate a new canvas object. This will ensure that each chart has its own unique space in the DOM.

Here’s how to do it in code:

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

Update Your HTML:
Ensure that you have a container in your HTML for holding these canvas elements:

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

Modify Your Chart Creation Function:
Then, update your existing chart creation function to ensure it utilizes the newly created canvas rather than a persistent or static one.

Here’s the relevant part of your code showing how to initiate the line chart:

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

Explanation of Key Sections

Canvas Creation: Each time you create a chart, ensure you append a new canvas element to the chartcontent section. This way, each chart will reference its unique canvas element, preventing data overwriting.

Animation onComplete Callback: This segment handles the tasks to be executed once the chart animation is complete. By storing the base64 image output of the chart directly to your image list (imageliste), you ensure that you can access the image data corresponding to the specific dataset used.

Conclusion

By following these steps, you should now be able to generate an indefinite number of charts in JavaScript using Chart.js, while ensuring that each chart corresponds to the appropriate dataset from your database queries.

No longer will you see only the last queried data or receive the same image output for each chart. With the clear separation of canvas objects, your data management practices become more robust, allowing for smoother chart generation.

Happy coding, and may your charts be insightful and plentiful!