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I am new to d3 and I have been following tutorials from www.d3-graph-gallery.com . These tutorials have worked very well for me, however, when it comes to displaying tooltips when hovering over data, things are weird. This tutorial shows how to do this on a heatmap. As you can see, it creates the tooltip as a div and then adds a mouselistener to the data that will make the tooltip div appear at the correct position. This works fine on the d3-graph-gallery website.
Unfortunatelly, it works neither on my local browser nor on Jsfiddle: https://jsfiddle.net/vcfhnu4q/
<!DOCTYPE html>
<meta charset="utf-8">
<!-- Load d3.js -->
<script src="https://d3js.org/d3.v6.js"></script>
<!-- Create a div where the graph will take place -->
<div id="my_dataviz"></div>
<script>
// set the dimensions and margins of the graph
const margin = {top: 30, right: 30, bottom: 30, left: 30},
width = 450 - margin.left - margin.right,
height = 450 - margin.top - margin.bottom;
// append the svg object to the body of the page
const svg = d3.select("#my_dataviz")
.append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", `translate(${margin.left},${margin.top})`);
// Labels of row and columns
const myGroups = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J"]
const myVars = ["v1", "v2", "v3", "v4", "v5", "v6", "v7", "v8", "v9", "v10"]
// Build X scales and axis:
const x = d3.scaleBand()
.range([ 0, width ])
.domain(myGroups)
.padding(0.01);
svg.append("g")
.attr("transform", `translate(0, ${height})`)
.call(d3.axisBottom(x))
// Build X scales and axis:
const y = d3.scaleBand()
.range([ height, 0 ])
.domain(myVars)
.padding(0.01);
svg.append("g")
.call(d3.axisLeft(y));
// Build color scale
const myColor = d3.scaleLinear()
.range(["white", "#69b3a2"])
.domain([1,100])
//Read the data
d3.csv("https://raw.githubusercontent.com/holtzy/D3-graph-gallery/master/DATA/heatmap_data.csv").then( function(data) {
// create a tooltip
const tooltip = d3.select("#my_dataviz")
.append("div")
.style("opacity", 0)
.attr("class", "tooltip")
.style("background-color", "white")
.style("border", "solid")
.style("border-width", "2px")
.style("border-radius", "5px")
.style("padding", "5px")
// Three function that change the tooltip when user hover / move / leave a cell
const mouseover = function(event,d) {
tooltip.style("opacity", 1)
}
const mousemove = function(event,d) {
tooltip
.html("The exact value of<br>this cell is: " + d.value)
.style("left", (event.x)/2 + "px")
.style("top", (event.y)/2 + "px")
}
const mouseleave = function(d) {
tooltip.style("opacity", 0)
}
// add the squares
svg.selectAll()
.data(data, function(d) {return d.group+':'+d.variable;})
.enter()
.append("rect")
.attr("x", function(d) { return x(d.group) })
.attr("y", function(d) { return y(d.variable) })
.attr("width", x.bandwidth() )
.attr("height", y.bandwidth() )
.style("fill", function(d) { return myColor(d.value)} )
.on("mouseover", mouseover)
.on("mousemove", mousemove)
.on("mouseleave", mouseleave)
})
</script>
If you look at the jsfiddle, you will see that the tooltip is placed at the bottom of the page, not next to the mouse when hovering over a cell, which makes sense to me, how would it be possible to draw the div on top of the svg ? Aren't they be separate containers?
How to get this to work?
236
asked Oct 17 '25 00:10
Your tooltip needs to have position style. Try this:
// create a tooltip
const tooltip = d3.select("#my_dataviz")
.append("div")
.style("opacity", 0)
.attr("class", "tooltip")
.style("background-color", "white")
.style("border", "solid")
.style("border-width", "2px")
.style("border-radius", "5px")
.style("padding", "5px")
.style("position", "absolute")
<!DOCTYPE html>
<meta charset="utf-8">
<!-- Load d3.js -->
<script src="https://d3js.org/d3.v6.js"></script>
<!-- Create a div where the graph will take place -->
<div id="my_dataviz"></div>
<script>
// set the dimensions and margins of the graph
const margin = {top: 30, right: 30, bottom: 30, left: 30},
width = 450 - margin.left - margin.right,
height = 450 - margin.top - margin.bottom;
// append the svg object to the body of the page
const svg = d3.select("#my_dataviz")
.append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", `translate(${margin.left},${margin.top})`);
// Labels of row and columns
const myGroups = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J"]
const myVars = ["v1", "v2", "v3", "v4", "v5", "v6", "v7", "v8", "v9", "v10"]
// Build X scales and axis:
const x = d3.scaleBand()
.range([ 0, width ])
.domain(myGroups)
.padding(0.01);
svg.append("g")
.attr("transform", `translate(0, ${height})`)
.call(d3.axisBottom(x))
// Build X scales and axis:
const y = d3.scaleBand()
.range([ height, 0 ])
.domain(myVars)
.padding(0.01);
svg.append("g")
.call(d3.axisLeft(y));
// Build color scale
const myColor = d3.scaleLinear()
.range(["white", "#69b3a2"])
.domain([1,100])
//Read the data
d3.csv("https://raw.githubusercontent.com/holtzy/D3-graph-gallery/master/DATA/heatmap_data.csv").then( function(data) {
// create a tooltip
const tooltip = d3.select("#my_dataviz")
.append("div")
.style("opacity", 0)
.attr("class", "tooltip")
.style("background-color", "white")
.style("border", "solid")
.style("border-width", "2px")
.style("border-radius", "5px")
.style("padding", "5px")
.style("position", "absolute")
// Three function that change the tooltip when user hover / move / leave a cell
const mouseover = function(event,d) {
tooltip.style("opacity", 1)
}
const mousemove = function(event,d) {
tooltip
.html("The exact value of<br>this cell is: " + d.value)
.style("left", (event.x)/2 + "px")
.style("top", (event.y)/2 + "px")
}
const mouseleave = function(d) {
tooltip.style("opacity", 0)
}
// add the squares
svg.selectAll()
.data(data, function(d) {return d.group+':'+d.variable;})
.enter()
.append("rect")
.attr("x", function(d) { return x(d.group) })
.attr("y", function(d) { return y(d.variable) })
.attr("width", x.bandwidth() )
.attr("height", y.bandwidth() )
.style("fill", function(d) { return myColor(d.value)} )
.on("mouseover", mouseover)
.on("mousemove", mousemove)
.on("mouseleave", mouseleave)
})
</script>Edit: Future advice - use Firefox Developer Edition. It has really good CSS style inspection tools like:
102
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