how to express a queue of Promise in d3 v5

问题

I have already read these answers, but I wasn't able to solve:

Adapt old geo to D3 v5, how to express a queue of Promise?

d3.js v5 - Promise.all replaced d3.queue

My code in d3 v4 looks like

d3.queue()
  .defer(d3.json, "path/file.json")
  .defer(populate,map,data)
  .await(ready);
}
function populate(map,data,callback) {
  .. code ..
  callback(null);

}

function ready(error, topo) {
  .. code ..
    }

I would like to replace this with Promise

回答1:

I'm assuming your populate function returns topo. You can use promise chaining:

function populate(map, data) {
  .. code ..
  return // return topo?
}

function ready(topo) {
  // map
  .. code ..
}
    
Promise.all([d3.json("path/file.json")])
  .then(([data]) => populate(map, data))
  .then(topo => {
    ready(topo)
  })

Instead of doing continuation using a callback, you can return the value normally, and it'll be picked up by the next function in the chain.

来源：https://stackoverflow.com/questions/62952888/how-to-express-a-queue-of-promise-in-d3-v5