如何在d3 v5中表达Promise队列 [英] how to express a queue of Promise in d3 v5

问题描述

我已经阅读了这些答案，但无法解决:

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

适应旧的地理位置D3 v5中，如何表达Promise队列?

d3.js v5-Promise.all已替换d3.queue

我在d3 v4中的代码如下

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 ..
    }

我想用Promise代替

I would like to replace this with Promise

推荐答案

我假设您的populate函数返回topo.您可以使用承诺链:

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)
  })

您可以正常返回该值，而无需使用回调来继续操作，并且该值将由链中的下一个函数获取.

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.

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