The brush.on() function in D3.js is used to set the event listener for the specified typenames and returns the brush.
Syntax:
brush.on( typenames, listener )Parameters:
This function accepts two parameters as mentioned above and described below:
- typenames: It is the string containing one or more typenames separated by whitespace.
- listener: It is the function to be used as the event listener for the specified typenames. It is an optional parameter.
Return Value:
This function returns the brush to be used.
Below programs illustrate the brush.on() function in D3.js:
Example 1:
<!DOCTYPE html>
<html>
<head>
<script src=
"https://d3js.org/d3.v4.min.js">
</script>
</head>
<body>
<center>
<h1 style="color: green;">
GeeksforGeeks
</h1>
<h3>D3.js brush.on() Function </h3>
<p style="color: green;">Center Point:</p>
<p style="color: green;" id="p"></p>
<svg width="300" height="300" id="brush">
</svg>
</center>
<script>
// Select the SVG element
d3.select("#brush")
// Create a brush
.call(d3.brush()
// Use the brush.on() function
// to set the given event listener
.on("brush", geekBrush)
.extent([[0, 0],
[300, 300]]
)
);
function geekBrush() {
const sel = d3.brushSelection(this);
// Select the paragraph element
var p = document.getElementById("p");
// Calculate the center point
// to be displayed
var pt1 = sel[1][0] - sel[0][0];
var pt2 = sel[1][1] - sel[0][1];
p.innerHTML = "( "
+ pt1 + ", " + pt2 + " )";
}
</script>
</body>
</html>
Output:
Example 2:
<!DOCTYPE html>
<html>
<head>
<script src=
"https://d3js.org/d3.v4.min.js">
</script>
<style>
circle {
fill-opacity: 0.2;
}
circle.active {
fill-opacity: 0.8;
stroke: green;
fill: red;
}
</style>
</head>
<body>
<center>
<h1 style="color:green;">GeeksforGeeks</h1>
<h3>D3.js | brush.on() Function </h3>
<svg width="400" height="200"></svg>
<script>
var data = d3.range(25).map(Math.random);
// Select the SVG element
var svg = d3.select("svg"),
margin = {
top: 0, right: 50,
bottom: 50, left: 50
},
width = svg.attr("width") -
margin.left - margin.right,
height = svg.attr("height") -
margin.top - margin.bottom,
g = svg.append("g")
.attr("transform", "translate("
+ margin.left + "," + margin.top + ")"
);
var x = d3.scaleLinear().range([0, width]),
y = d3.randomNormal(height / 2, height / 8);
var brush = d3.brushX()
// Use the brush.on() function
// to set the given event listener
.on("start brush end", brushmoved)
.extent([[0, 0], [width, height]]);
var circle = g.append("g")
.attr("class", "circle")
.selectAll("circle")
.data(data)
.enter().append("circle")
.attr("transform", function (d) {
return "translate("
+ x(d) + "," + y() + ")";
})
.attr("r", 10);
var gBrush = g.append("g")
.attr("class", "brush")
.call(brush);
gBrush.call(brush.move, [0.3, 0.5].map(x));
var bs = "";
// Define the function to be
// called when the brush is moved
function brushmoved() {
var s = d3.event.selection;
if (s == null) {
handle.attr("display", "none");
circle.classed("active", false);
} else {
var sx = s.map(x.invert);
circle.classed("active", function (d) {
return sx[0] <= d && d <= sx[1];
});
handle.attr("display", null)
.attr("transform", function (d, i) {
return "translate("
+ s[i] + "," + height / 2 + ")";
});
}
}
</script>
</center>
</body>
</html>
Output:
