How to customise event listeners in d3.js?

@denis 

In d3.js, you can customise event listeners by creating custom functions that define how you want to handle the events. Here is a general approach to customising event listeners in d3.js:

1. Select the element you want to add an event listener to using d3.select() or d3.selectAll().
2. Use the .on() method to add an event listener to the selected element. The .on() method takes two arguments: the event type (e.g., "click", "mouseover", "mouseout") and the custom function that you want to execute when the event is triggered.
3. Define a custom function that specifies what should happen when the event is triggered. This function can include any number of actions you want to take, such as changing the style of the element, updating data, or triggering other events.

Here is an example of customising an event listener in d3.js:

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// Select the element
const circle = d3.select("#my-circle");

// Add an event listener
circle.on("click", function() {
  // Custom function for click event
  d3.select(this)
    .attr("fill", "red")
    .attr("r", 10);
});

In this example, we select a circle element with the ID "my-circle" and add a click event listener to it. When the circle is clicked, the custom function is executed, changing the fill color to red and the radius to 10. This is just a simple example, and you can customise event listeners to suit your specific needs.