Text inside non-transparent rectangle is not visible - d3.js

Question

I have the following segment in one of my d3 graph.
What I want is to display some text in a rectangle.
var values = $('#<%=hdnDtArray.ClientID%>').val();
var data = JSON.parse(values);
margin = {
top: 20,
right: 60,
bottom: 20,
left: 100
};
var width = 900,
height = 350;
var vis = d3.select("#line_chart").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom);
var parseTime = d3.time.format("%Y.%m.%d").parse;
max_y = 0;
min_y = data[0].close;
var extent = d3.extent(data.map(function(d) {
return d.date
}));
max_x = extent[1];
min = extent[0];
for (i = 0; i < data.length; i++) {
max_y = Math.max(max_y, data[i].close);
min_y = Math.min(min_y, data[i].close);
}
var x = d3.time.scale()
.rangeRound([margin.left, width]);
xScale = x.domain(d3.extent(data, function(d) {
return parseTime(d.date);
}));
yScale = d3.scale.linear().range([height - margin.top, margin.bottom]).domain([0, max_y]),
xAxis = d3.svg.axis()
.scale(xScale),
yAxis = d3.svg.axis()
.scale(yScale)
.orient("left")
.innerTickSize(-width + margin.left)
.outerTickSize(0)
.tickPadding(10);
vis.append("svg:g")
.attr("class", "x axis")
.style({
'stroke': 'Black',
'fill': 'none',
"stroke-width": 1,
"font-size": "13px"
})
.attr("transform", "translate(0," + (height - margin.bottom) + ")")
.call(xAxis)
.selectAll("text")
.attr("transform", "translate(-10,0) rotate(-40)")
.style("text-anchor", "end");
vis.append("text")
.attr("class", "x label")
.attr("text-anchor", "end")
.attr("x", width + 120)
.attr("y", height - 10)
.attr("font-weight", "bold");
vis.append("svg:g")
.attr("class", "y axis")
.style({
'stroke': 'Black',
'fill': 'none',
'stroke-width': 1,
"font-size": "13px"
})
.attr("transform", "translate(" + (margin.left) + ",0)")
.call(yAxis);
vis.append("text")
.attr("class", "y label")
.attr("text-anchor", "end")
.attr("x", margin.left + 5)
.attr("y", margin.top - 2)
.attr("font-weight", "bold");
var line = d3.svg.line()
.x(function(d) {
return xScale(parseTime(d.date));
})
.y(function(d) {
return yScale(d.close);
})
.interpolate("basis");
vis.append('svg:path')
.datum(data)
.attr("fill", "none")
.attr("stroke", "steelblue")
.attr("stroke-linejoin", "round")
.attr("stroke-linecap", "round")
.attr("stroke-width", 1.5)
.attr("d", line);
var hoverLineGroup = vis.append("g")
.attr("class", "hover-line");
var hoverLine = hoverLineGroup.append("line")
.attr("stroke", "#000000")
.attr("stroke-width", "1px")
.attr("x1", 10).attr("x2", 10)
.attr("y1", 20).attr("y2", height - 20);
var hoverTT = hoverLineGroup.append('text')
.attr("class", "hover-tex capo")
.attr('dy', "0.35em");
var cle = hoverLineGroup.append("circle")
.attr("r", 4.5);
var hoverTT2 = hoverLineGroup.append('text')
.attr("class", "hover-text capo")
.attr('dy', "0.55em");
hoverLineGroup.style("opacity", 1e-6);
var rectHover = vis.append("rect")
.data(data)
.attr("fill", "none")
.attr("width", width)
.attr("height", height);
var hoverCircle = hoverLineGroup.append("circle");
var hoverRect = hoverLineGroup
.append("rect");
vis.on("mouseout", hoverMouseOff)
.on("mousemove", hoverMouseOn);
var bisectDate = d3.bisector(function(d) {
return parseTime(d.date);
}).left;
function hoverMouseOn() {
var mouse_x = d3.mouse(this)[0];
var mouse_y = d3.mouse(this)[1];
var graph_y = yScale.invert(mouse_y);
var graph_x = xScale.invert(mouse_x);
var mouseDate = xScale.invert(mouse_x);
var i = bisectDate(data, mouseDate);
var d0 = data[i - 1]
var d1 = data[i];
var d = mouseDate - d0[0] > d1[0] - mouseDate ? d1 : d0;
hoverRect.attr("class", "y")
.style("fill", "none")
.style("stroke", "black")
.attr('x', mouse_x + 8)
.attr('y', yScale(d.close) - 20)
.attr("width", 200)
.attr("height", 50);
hoverTT.text("Test Text")
.attr("opacity", "1");
hoverTT.attr('x', mouse_x + 23);
hoverTT.attr('y', yScale(d.close));
/*
hoverTT.text("Date: " + d.date);
hoverTT.attr('x', mouse_x + 23);
hoverTT.attr('y', yScale(d.close));
hoverTT2.text("Portfolio Value: " + Math.round(d.close * 100) / 100)
.attr('x', mouse_x + 23)
.attr('y', yScale(d.close) + 10);
*/
hoverLine.attr("x1", mouse_x).attr("x2", mouse_x)
hoverLineGroup.style({
'font-weight': 'bold',
'opacity': 1
});
hoverCircle.attr("class", "y")
.style("fill", "blue")
.style("stroke", "blue")
.attr("r", 4)
.attr('cx', mouse_x)
.attr('cy', yScale(d.close));
}
function hoverMouseOff() {
hoverLineGroup.style("opacity", 1e-6);
}
The text is not visible now. But if I set the "fill" property to "none", then the text becomes visible.
What I want is the background to be non transparent, that's why I made it white.
Still I want the text to be visible.

Answer 1

The problem with your code is the order of the selections.
In an SVG, just like a real painter using ink in a real canvas, what is painted later remains on top. So, if you want the text to be on top of the rectangle (with any fill you want), set the text's selection after the rectangle's selection.
Therefore, in your case, this...
var hoverTT = hoverLineGroup.append('text')
.attr("class", "hover-tex capo")
.attr('dy', "0.35em");
... has to be after this:
var hoverRect = hoverLineGroup
.append("rect");
Here is a demo, the rectangle has a solid white fill. Have a look at the order of the selections:
var svg = d3.select("svg");
var hoverRect = svg.append("rect")
.attr("fill", "white")
.attr("stroke", "firebrick")
.attr("width", 40)
.attr("height", 30)
.attr("opacity", 0);
var hoverText = svg.append("text")
.text("foo")
svg.on("mousemove", function() {
var coords = d3.mouse(this);
hoverRect.attr("x", coords[0] + 15)
.attr("y", coords[1])
.attr("opacity", 1)
hoverText.attr("x", coords[0] + 25)
.attr("y", coords[1] + 20)
})
svg {
border: 1px solid gray;
background-color: gainsboro;
}
<script src="https://d3js.org/d3.v4.min.js"></script>
<svg></svg>