d3 adding data attribute conditionally

Question

I\'m creating a table with d3 to be used by the FooTable jquery plugin and this requires having some data- attributes in the header row. But not all columns have all the data a

Answer 1

The most voted solution is perfect because .attr(a,b) works as conditional when b is null,

 d3chain.attr('data-class', d=>'data-class' in d ? d['data-class'] : null );

but this solution is not geral, is not valid for other chaining methods, except using .each(), .filter or .call(). In general the most simple is call().

.call(condFunc,param)

Suppose that param is an global variable used as parameter in the condition, and that g is a global object used to return a value.

  // inconditional
  d3chain.attr(param, g[param])

  // conditional case using globals
  d3chain.call( s => { if (g[param]) s.attr(param,g[param]) })

  // conditional case passing the parameter
  d3chain.call( (s,p) => {
     if (g[p]) s.attr(p, g[p])
  }, param)

.each(d => condFunc)

Typical use:

 d3chain.each( d=> {
     if (param && d) d3.select(this).attr(d, g[param])
 })

See @nrabinowitz answer for detailed example.

.filter(d=>condFunc).etc

Typical use:

 d3chain.filter( d=> param in d ).attr(param, d=> g[param])

See @LarsKotthoff answer for detailed example.