How To Reuse Two (or More) Sequences Of Chained Transitions In D3

I have to apply two very long sequences of chained transitions, which differ mainly on the order of transitions, and I'm looking for a compact way to code. As a toy example, consi

Solution 1:

As noted in the comments, the principles for answering this question are the same as your previous question. In this case, you have a set of different transitions that might be applied in any order referred to by different keys. Let's store them in an object:

var transitions = {
  a: function(sel){ return sel.transition().duration(1000).delay(1000).attr('cy', 200) },
  b: function(sel){ return sel.transition().duration(2000).delay(0).attr('r', 40) },
  c: function(sel){ return sel.transition().duration(500).delay(1500).attr('fill', 'red') },
  d: function(sel){ return sel.transition().duration(1500).delay(500).attr('opacity', 0.5) },
  e: function(sel){ return sel.transition().duration(1000).delay(3000).attr('cy', 300) },
  f: function(sel){ return sel.transition().duration(2000).delay(0).attr('r', 60) },
  g: function(sel){ return sel.transition().duration(500).delay(1500).attr('fill', 'magenta') },
  h: function(sel){ return sel.transition().duration(1500).delay(500).attr('opacity', 0.25) }
};

Each function takes a d3.selection object and applies specific transition parameters and sets of transformations to it. These functions can be as long and complicated as you like. I am lazy with little imagination so they only do one transformation in this version.

There's already a bit of code repetition here, so let's take out the conversion of the selection to a transition, and use this instead of passing an argument:

var transitions = {
  a: function(){ returnthis.duration(1000).delay(1000).attr('cy', 200) },
  b: function(){ returnthis.duration(2000).delay(0).attr('r', 40) },
  c: function(){ returnthis.duration(500).delay(1500).attr('fill', 'red') },
  d: function(){ returnthis.duration(1500).delay(500).attr('opacity', 0.5) },
  e: function(){ returnthis.duration(1000).delay(3000).attr('cy', 300) },
  f: function(){ returnthis.duration(2000).delay(0).attr('r', 60) },
  g: function(){ returnthis.duration(500).delay(1500).attr('fill', 'magenta') },
  h: function(){ returnthis.duration(1500).delay(500).attr('opacity', 0.25) }
};

Now we can perform these transitions by calling code like

transitions['a'].call( selection.transition() )
transitions.f.call( d3.select('circle').transition() )

You want to specify an array of transitions to apply to a selection, something like this:

apply_transitions( group.select(":nth-child(1)"), ['a','b','c','d'] );
apply_transitions( group.select(":nth-child(2)"), ['e','f','g','h'] );

This could be implemented as follows:

/**
* apply a series of transitions to a selection
*
* @param selection - d3 selection
* @param tr_arr - array of transition identifiers, referring to functions in the `transitions` object
*/
function apply_transitions( selection, tr_arr ) {

  // turn the current selection into a d3.transition// call the transition function referred to by the first ID in the array// with the d3.transition as the `this` context// note that the function returns a transition object, so it can be chained
  transitions[ tr_arr[0] ].call( selection.transition() )
  // add a handler to be applied at the end of the transition.on('end', function(){
      // if there are more transitions to be applied, call// apply_transitions again with tr_arr minus the first element// note that the `this` context in the `on` function is a DOM element,// so use `d3.select(this)` to turn it into a d3 selection
      if ( tr_arr.length > 1 ) {
        apply_transitions( d3.select(this), tr_arr.slice(1) );
      }
    })
}

Live action example:

var svg = d3.select('svg').attr('width', 500).attr('height', 500);

    var dataSet = [20, 20];

    var group=svg.append("g");
    var circles = group.selectAll('circle')
    .data(dataSet)
    .enter()
    .append('circle')
    .attr("r",function(d){ return d })
    .attr("cx",function(d, i){ return i * 100 + 50 })
    .attr("cy",50)
    .attr("fill",'black');

    apply_transitions( group.select(":nth-child(1)"), ['a','b','c','d'] );

    apply_transitions( group.select(":nth-child(2)"), ['e','f','g','h'] );

  functionapply_transitions( selection, tr_arr ) {

    var transitions = {
      a: function(){ returnthis.duration(1000).delay(1000).attr('cy', 200) },
      b: function(){ returnthis.duration(2000).delay(0).attr('r', 40) },
      c: function(){ returnthis.duration(500).delay(1500).attr('fill', 'red') },
      d: function(){ returnthis.duration(1500).delay(500).attr('opacity', 0.5) },
      e: function(){ returnthis.duration(1000).delay(3000).attr('cy', 300) },
      f: function(){ returnthis.duration(2000).delay(0).attr('r', 60) },
      g: function(){ returnthis.duration(500).delay(1500).attr('fill', 'magenta') },
      h: function(){ returnthis.duration(1500).delay(500).attr('opacity', 0.25) }
    };

      transitions[ tr_arr[0] ].call( selection.transition() )
        .on('end', function(){
          if ( tr_arr.length > 1 ) {
            apply_transitions( d3.select(this), tr_arr.slice(1) );
          }
        })
  }

<scriptsrc="http://d3js.org/d3.v5.js"></script><svg></svg>