score:73

Accepted answer

d3.select(this).node() is the same as just this in the context of a function passed to a D3 selection. You could rework it like this d3.select(this.parentNode).datum() and get the correct value back without having to use the ugly double-underscore property.

score:8

I found this post when I had exactly the same issue. My solution, was to change the selection to pass on the data that I will need in the child, which I think might be a valid approach if you can live with the data redundancy in the node.

[
  {
    title: "Google",
    link: "www.google.com",
    languagePath : "en,fr,it"
  },

  ...
]

To help explain, I've used this in the context of a table, with two columns. The first column has the title and the second column has an a for each of the accept-language items.

So I did a sub selections of the split of languagePath and for each enter call, I would create a a with the text being the language.

So at this point I also need the link, so that the a elements look like:

<a href="www.google.com/en">EN</a>
<a href="www.google.com/fr">FR</a>

But the link is not part of the data passed to this child, so when I did the selection instead of doing:

var langLinks = tableRow
     .append("td")
     .selectAll("span")
     .data(function(d) {
        return d.languagePath.split(",")
      })

I did

 var langLinks = tableRow
     .append("td")
     .selectAll("span")
     .data(function(d) {
        return d.languagePath.split(",").map(function(item) {
                 return {
                   lang : item,
                   link : d.link
               })
      })

And so, when I'm processing data on the enter() of this selection I do have the parent's data.

Hope this is a valid alternative for some of you, it did help me.

score:23

The other method I'm familiar with is to use .each() on the parent, and then deal with children within the closure:

d3.selectAll('.parent').each(function(parentDatum) {
    d3.select(this).selectAll('.child').each(function(childDatum) {
        // do stuff with parentDatum and childDatum here
    });
});

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