How to create dropdown list and bind with data coming from server

Question

I am very new to Angular. I have got some work on Angular.

I need to bind Nested dropdown list for Json data which is coming from server by calling Rest Api.

Data has one attribute Level, Specifies the level in the hierarchy of the group. Parent will have Immediate Child=1, Grandchild=2 and so on. Child and Grandchild has Group field, which shows inside which parent menu, child menu will be there.

I have tried it to develop but I found all examples of bootstrap with static data in html file and separate CSS file which was complicated to me.

I want to do it dynamically using TypeScript. How can I start working on it.

Answer 1

This is a sample coded which you need as per nested level data from your json data. Now you can for loop the formatted json data in the DOM using model data. I hope this will help you out create a multi-level drop-down

groupBy(xs, key) {
   return xs.reduce(function (rv, x) {
     (rv[x[key]] = rv[x[key]] || []).push(x);
    return rv;
   }, {});
 }

var model;

getData() {
 var   sampleData = {
  "ArrayOfLocationGroup": {
    "LocationGroup": [
      ...
      ...//Server response data
      ],
    "_xmlns:xsd": "http://www.w3.org/2001/XMLSchema"
  }
 }    

var list = this.sampleData["ArrayOfLocationGroup"]["LocationGroup"];
var formattedList = [];

list.forEach(element => {

  var obj = {  //Make sure your server response data to like this structure
    "Id": element.Id,
    "Name": element.Name,
    "GroupId": element.GroupId.__text,
    "ParentLocationGroup": element.ParentLocationGroup.__text,
    "LgLevel": element.LgLevel.__text,
    "Child" : []
  }
  formattedList.push(obj);
});

var groupDataList = this.groupBy(formattedList, "LgLevel");

var parents = groupDataList[0];
var child = groupDataList[1];
var childOfChild = groupDataList[2];

child.forEach(c => {
  c.Child = childOfChild.filter(x => x.ParentLocationGroup == c.Id);
})

parents.forEach(p => {
  p.Child = child.filter(x => x.ParentLocationGroup == p.Id);
})

this.model = parents;
}

Html File

    <ul class="nav site-nav">
     <li class=flyout>
      <a href=#>Dropdown</a>
      <!-- Flyout -->
      <ul class="flyout-content nav stacked">
        <li *ngFor="let parent of model" [class.flyout-alt]="parent.Child.length > 0"><a href=#>{{parent.Name}}</a>
          <ul *ngIf="parent.Child.length > 0" class="flyout-content nav stacked">
            <li *ngFor="let c of parent.Child" [class.flyout-alt]="c.Child.length > 0"><a href=#>{{c.Name}}</a>
              <ul *ngIf="c.Child.length > 0" class="flyout-content nav stacked">
                <li *ngFor="let cc of c.Child" [class.flyout-alt]="cc.Child.length > 0"><a href=#>{{cc.Name}}</a></li>
              </ul>
            </li>
          </ul>
        </li>
      </ul>
    </li>
  </ul>

As per your server response data organize the model data. Response json format changed (__text to #text)

 var obj = {
    "Id": element.Id,
    "Name": element.Name && element.Name.#text ? element.Name.#text : element.Name,
    "GroupId": element.GroupId && element.GroupId.#text ? element.GroupId.#text : element.GroupId,
    "ParentLocationGroup": element.ParentLocationGroup && element.ParentLocationGroup.#text ? element.ParentLocationGroup.#text : element.ParentLocationGroup,
    "LgLevel": element.LgLevel && element.LgLevel.#text ? element.LgLevel.#text : element.LgLevel,
    "Child" : []
  }