discourse/app/assets/javascripts/admin/components/value-list.js.es6

export default Ember.Component.extend({
  classNameBindings: [":value-list"],

  _enableSorting: function() {
    const self = this;
    const placeholder = document.createElement("div");
    placeholder.className = "placeholder";

    let dragging = null;
    let over = null;
    let nodePlacement;

    this.$().on("dragstart.discourse", ".values .value", function(e) {
      dragging = e.currentTarget;
      e.dataTransfer.effectAllowed = "move";
      e.dataTransfer.setData("text/html", e.currentTarget);
    });

    this.$().on("dragend.discourse", ".values .value", function() {
      Ember.run(function() {
        dragging.parentNode.removeChild(placeholder);
        dragging.style.display = "block";

        // Update data
        const from = Number(dragging.dataset.index);
        let to = Number(over.dataset.index);
        if (from < to) to--;
        if (nodePlacement === "after") to++;

        const collection = self.get("collection");
        const fromObj = collection.objectAt(from);
        collection.replace(from, 1);
        collection.replace(to, 0, [fromObj]);
        self._saveValues();
      });
      return false;
    });

    this.$().on("dragover.discourse", ".values", function(e) {
      e.preventDefault();
      dragging.style.display = "none";
      if (e.target.className === "placeholder") {
        return;
      }
      over = e.target;

      const relY = e.originalEvent.clientY - over.offsetTop;
      const height = over.offsetHeight / 2;
      const parent = e.target.parentNode;

      if (relY > height) {
        nodePlacement = "after";
        parent.insertBefore(placeholder, e.target.nextElementSibling);
      } else if (relY < height) {
        nodePlacement = "before";
        parent.insertBefore(placeholder, e.target);
      }
    });
  }.on("didInsertElement"),

  _removeSorting: function() {
    this.$()
      .off("dragover.discourse")
      .off("dragend.discourse")
      .off("dragstart.discourse");
  }.on("willDestroyElement"),

  _setupCollection: function() {
    const values = this.get("values");
    if (this.get("inputType") === "array") {
      this.set("collection", values || []);
    } else {
      this.set("collection", values && values.length ? values.split("\n") : []);
    }
  }
    .on("init")
    .observes("values"),

  _saveValues: function() {
    if (this.get("inputType") === "array") {
      this.set("values", this.get("collection"));
    } else {
      this.set("values", this.get("collection").join("\n"));
    }
  },

  inputInvalid: Ember.computed.empty("newValue"),

  keyDown(e) {
    if (e.keyCode === 13) {
      this.send("addValue");
    }
  },

  actions: {
    addValue() {
      if (this.get("inputInvalid")) {
        return;
      }

      this.get("collection").addObject(this.get("newValue"));
      this.set("newValue", "");

      this._saveValues();
    },

    removeValue(value) {
      const collection = this.get("collection");
      collection.removeObject(value);
      this._saveValues();
    }
  }
});