source: node_modules/d3-transition/src/transition/style.js@ e4c61dd

import {interpolateTransformCss as interpolateTransform} from "d3-interpolate";
import {style} from "d3-selection";
import {set} from "./schedule.js";
import {tweenValue} from "./tween.js";
import interpolate from "./interpolate.js";

function styleNull(name, interpolate) {
  var string00,
      string10,
      interpolate0;
  return function() {
    var string0 = style(this, name),
        string1 = (this.style.removeProperty(name), style(this, name));
    return string0 === string1 ? null
        : string0 === string00 && string1 === string10 ? interpolate0
        : interpolate0 = interpolate(string00 = string0, string10 = string1);
  };
}

function styleRemove(name) {
  return function() {
    this.style.removeProperty(name);
  };
}

function styleConstant(name, interpolate, value1) {
  var string00,
      string1 = value1 + "",
      interpolate0;
  return function() {
    var string0 = style(this, name);
    return string0 === string1 ? null
        : string0 === string00 ? interpolate0
        : interpolate0 = interpolate(string00 = string0, value1);
  };
}

function styleFunction(name, interpolate, value) {
  var string00,
      string10,
      interpolate0;
  return function() {
    var string0 = style(this, name),
        value1 = value(this),
        string1 = value1 + "";
    if (value1 == null) string1 = value1 = (this.style.removeProperty(name), style(this, name));
    return string0 === string1 ? null
        : string0 === string00 && string1 === string10 ? interpolate0
        : (string10 = string1, interpolate0 = interpolate(string00 = string0, value1));
  };
}

function styleMaybeRemove(id, name) {
  var on0, on1, listener0, key = "style." + name, event = "end." + key, remove;
  return function() {
    var schedule = set(this, id),
        on = schedule.on,
        listener = schedule.value[key] == null ? remove || (remove = styleRemove(name)) : undefined;

    // If this node shared a dispatch with the previous node,
    // just assign the updated shared dispatch and we’re done!
    // Otherwise, copy-on-write.
    if (on !== on0 || listener0 !== listener) (on1 = (on0 = on).copy()).on(event, listener0 = listener);

    schedule.on = on1;
  };
}

export default function(name, value, priority) {
  var i = (name += "") === "transform" ? interpolateTransform : interpolate;
  return value == null ? this
      .styleTween(name, styleNull(name, i))
      .on("end.style." + name, styleRemove(name))
    : typeof value === "function" ? this
      .styleTween(name, styleFunction(name, i, tweenValue(this, "style." + name, value)))
      .each(styleMaybeRemove(this._id, name))
    : this
      .styleTween(name, styleConstant(name, i, value), priority)
      .on("end.style." + name, null);
}