D3 - Update pattern in stacked area chart

问题

I have a demo here

It's a D3 stacked area chart within an Angular app.

I wanted to have a D3 Update pattern in this chart put I can't get it to work using the normal method I use.

This doesn't seem to work.

areaGroup.selectAll('path')
    .data(data)

areaGroup   
    .enter()
    .append('path')
    .attr('class', (d, i) => 'path_'+(i+1) )
    .attr('d', areaGenerator)

How can I use the General Update Pattern with a Stacked Area Chart

来源：https://stackoverflow.com/questions/56872020/d3-update-pattern-in-stacked-area-chart