cell.exit().transition not a function

[AriaFallah]

I'm using d3 v4 with the new release

cell.exit().transition().style("opacity", 0).remove();

throws the error when I do .call(legend).

TypeError: cell.exit(...).transition is not a function

[AriaFallah]

d3-selection by itself does not have the .transition() function. All you need to do is

import 'd3-transition' // es6
require('d3-transition') 

at the top of your code to "inject" it into the selection API