Getting parent attributes from children in nested selections?

[Ed]

I have a stacked barchart that I produced with a nested selection/d3.nest datastructure and was wondering what the best idiom for
getting information about the parent (in this case the parent's index) from the child was. I'm using the following, which seems to work:

in the parent:

.attr( "data-idx", function( d, i ) { return( i ); } )

in the child which is nested inside two <g>'s:

var idx = +d3.select( this.parentNode.parentNode ).attr( "data-idx" );

Is this considered good form or is there a better way to do it?

[Chris Viau]

You can grab the parent index from a third argument in the accessor function: function(d, i, j){ /* j is the parent index */ };

Here I show 3 of the multiple ways of accessing parents data and index: http://jsfiddle.net/christopheviau/dHtMj/

Chris

[Ed]

So simple, thanks!

  - Ed

[Paulo Brito]

Hi, if I add a transition j returns undefined, is that the normal behavior?

.append("text").transition()
    .duration(2000)
    .attr({class: 'value', x: cellX, dy: '1em'})
    .text(function(d, i, j){
        console.log('Method A: Parent data: ', data[j], 'Parent index: ', j);
        console.log('Method B: Parent data: ', this.parentNode.__data__);                                  
        return d;
     });
Thanks,
Paulo Brito

[Chris Viau]

The j will probably only be available if you have a subselection. Can you share the rest of your code on bl.ocks, tributary or jsfiddle?

[Paulo Brito]

I made the changes to your code 

http://jsfiddle.net/paulosb/GcXrJ/

[Chris Viau]

Interesting