How can a node be zoomed in a D3 force graph?

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To zoom in on a node in a D3 force graph, follow these steps:

1. Import the D3 zoom library by adding the following code to your script:

var zoom = d3.zoom()
    .scaleExtent([0.5, 10])
    .on("zoom", zoomed);

1. Create a zoom function to handle the zooming event:

function zoomed() {
  svg.attr("transform", d3.event.transform);
}

1. Add the zoom behavior to the SVG element:

var svg = d3.select("svg")
    .call(zoom);

1. In the tick function that updates the positions of the nodes and links, add a transform attribute to the node as follows:

node.attr("transform", function(d) {
    return "translate(" + d.x + "," + d.y + ") " + "scale(" + d.scale + ")";
});

1. Add event listeners to the nodes to handle zooming:

node.on("mouseover", function(d) {
  d.scale = 1.5;
  update();
})
.on("mouseout", function(d) {
  d.scale = 1;
  update();
})

1. Finally, update the update function to apply the zoom behavior to the nodes:

function update() {
  // Update the nodes…
  node.attr("transform", function(d) {
      return "translate(" + d.x + "," + d.y + ") " + "scale(" + d.scale + ")";
  });

  // Update the links…
  link.attr("x1", function(d) { return d.source.x; })
      .attr("y1", function(d) { return d.source.y; })
      .attr("x2", function(d) { return d.target.x; })
      .attr("y2", function(d) { return d.target.y; });
}

When a user hovers over a node, it will be scaled up by a factor of 1.5, and when they mouse out, it will be scaled back down to 1. The update function will apply the zoom behavior to the nodes by updating their transform attribute with the current scale value.