Function filter not working as expected in d3js

Question

I have this HTML structure

<g class="type type-project" id="g-nsmart_city_lab" transform="translate(954.9537424482861,460.65694411587845)">
   <circle class="highlighter-circles" fill-opacity="0" r="70" fill="rgb(150,150,150)" id="hc-nsmart_city_lab"></circle>
   <circle class="node" r="50" fill="#768b83" id="nsmart_city_lab" filter="url(#blur)"></circle>
   <text font-family="Comic Sans MS" font-size="18px" fill="black" class="nodetext" id="t-nsmart_city_lab" style="text-anchor: middle;" x="0" y="0">SMART CITY LAB</text>
   <image href="./icons/project.svg" width="30" height="30" id="i-nsmart_city_lab" class="nodeimg"></image>
   <image href="./icons/expand2.svg" width="30" height="30" for-node="nsmart_city_lab" x="25" y="-45" id="ne-nsmart_city_lab" class="nodeexp" style="visibility: hidden;" data-expandable="false"></image>
   <circle class="inv_node" r="50" fill="red" fill-opacity="0" id="inv_nsmart_city_lab"></circle>
</g>

and I want to to something with the g elements that fulfill certain condition. But when doing,

d3.selectAll("g.type").filter(g_element => g_element.class !== "whatever");

the filter does not work as expected (at least for me). g_element.class is undefined . After debugging, for some reason the filtering is returning <circle class="node" r="50" fill="#768b83" id="nsmart_city_lab" filter="url(#blur)"></circle> instead of a g object to access its attributes and do the filtering.

How could this be done then ?

Here you have a jsfiddle which always returns undefined, https://jsfiddle.net/k6Ldxtof/40/

Answer 1

In your snippet...

d3.selectAll("g.type").filter(g_element => g_element.class !== "whatever");

... the first argument, which you named g_element , is the datum bound to that element. As there is no data bound here, that's obviously undefined .

To get the element instead, you have to use this . However, since you're using a arrow function here, you need to use the second and third arguments combined:

d3.selectAll("g.type")
    .filter((_,i,n) => console.log(n[i]))

Then to get the classes, you can simply use a getter...

d3.selectAll("g.type")
    .filter((_,i,n) => console.log(d3.select(n[i]).attr("class"))) 

Or, even simpler, using classList :

d3.selectAll("g.type")
    .filter((_, i, n) => console.log(n[i].classList))

Here is the demo:

 function create() { let g = d3.select("body") .append("svg") .attr("height", "500") .attr("width", "500") .append("g"); g.append("g") .attr("class", "type type-red") .attr("data-color", "red") .append("circle") .attr("r", 50) .attr("fill", "red") .attr("cx", 50) .attr("cy", 50); g.append("g") .attr("class", "type type-green") .attr("data-color", "green") .append("circle") .attr("r", 50) .attr("fill", "green") .attr("cx", 200) .attr("cy", 50); g.append("g") .attr("class", "type type-blue") .attr("data-color", "blue") .append("circle") .attr("r", 50) .attr("fill", "blue") .attr("cx", 100) .attr("cy", 150); filter_out(); } /***************** USING THE SELECTOR ********************/ function filter_out() { d3.selectAll("g.type") .filter((_, i, n) => console.log(n[i].classList)) .attr("opacity", 0.5); } create();

 <script src="https://d3js.org/d3.v4.js"></script>