How to display dropdowns based on another dropdown using typewriting in an Angular 2 application

Question

I am developing an Angular 2 application, in my current project I need functionality to display outliers based on year, brand, model. For example, if I choose Honda, then only Honda models are displayed in the drop-down list of models.

By default, I will link the full data for the year, make and model.

This is my view.

VehicleComponent.html

  <div class="row form-group">
                                    <div class="col-md-3">
                                        <label  class="control-label">Year*</label><br />
                                        <select  friendly-name="Year" id="year" name="year" class="col-md-6 form-control"  ng-required="true" onchange='OnChange()' >
                                            <option>Select</option>

                                            <option *ngFor='let type of lookupdetailsvehicleyearinfo'>{{type.LookupValue}}</option>

                                        </select>
                                    </div>
                                    <div class="col-md-3">
                                        <label  class="control-label">Make*</label><br />
                                        <select friendly-name="Make" class="col-md-6 form-control" ng-required="true" >
                                            <option>Select</option>
                                            <option *ngFor='let type of lookupdetailsvehiclemakeinfo'>{{type.LookupValue}}</option>
                                            </select>
                                    </div>
                                    <div class="col-md-3">
                                        <label  class="control-label">Model*</label>
                                        <select  friendly-name="Model" class="col-md-6 form-control" ng-required="true" >
                                            <option>Select</option>
                                            <option *ngFor='let type of lookupdetailsvehiclemodelinfo'>{{type.LookupValue}}</option>
                                           </select>
                                    </div>                                      
                                </div>

I will get the above data from My Own API's.

Please tell me how to write typewritten code in an angular 2 application for the above functionality.

Answer 1

, , - change - -. Angular2 .

value:

@Component({
  selector: 'my-app',
  template: `
    <div>
      <h2>Hello {{name}}</h2>

      <select (change)="firstDropDownChanged($event.target.value)" >
        <option>Select</option>
        <option *ngFor='let v of _values1'>{{ v }}</option>
      </select>

      <select >
        <option>Select</option>
        <option *ngFor='let v of _values2'>{{ v }}</option>
      </select>
    </div>
  `,
})
export class App {
  name:string;

  private _values1 = ["1", "2", "3"];
  private _values2 = [];

  constructor() {
    this.name = 'Angular2'
  }

  firstDropDownChanged(val: any) {
    console.log(val);

    if (val == "1") {
      this._values2 = ["1.1", "1.2", "1.3"];
    }
    else if (val == "2") {
      this._values2 = ["2.1", "2.2", "2.3"];
    }
    else if (val == "3") {
      this._values2 = ["3.1", "3.2", "3.3"];
    }
    else {
      this._values2 = [];
    }
  }
}

live-demo: https://plnkr.co/edit/GDXsPt4aiS7vus6oPvuU?p=preview

UPDATE

selectedIndex:  ( , -1 "Select" -item.

@Component({
  selector: 'my-app',
  template: `
    <div>
      <h2>Hello {{name}}</h2>

      <select (change)="firstDropDownChanged($event.target.selectedIndex - 1)" >
        <option>Select</option>
        <option *ngFor="let v of _values1">{{ v.val }}</option>
      </select>

      <select >
        <option>Select</option>
        <option *ngFor='let v of _values2'>{{ v }}</option>
      </select>
    </div>
  `,
})
export class App {
  name:string;

  private _values1 = [
    { id: 1, val: "huhu" },
    { id: 2, val: "val2" },
    { id: 3, val: "yep" },
    { id: 4, val: "cool" }
  ];
  private _values2 = [];

  constructor() {
    this.name = 'Angular2'
  }

  firstDropDownChanged(val: any) {
    const obj = this._values1[val];
    console.log(val, obj);

    if (!obj) return;

    if (obj.id == 1) {
      this._values2 = ["1.1", "1.2", "1.3"];
    }
    else if (obj.id == 2) {
      this._values2 = ["2.1", "2.2", "2.3"];
    }
    else if (obj.id == 3) {
      this._values2 = ["3.1", "3.2", "3.3"];
    }
    else {
      this._values2 = [];
    }
  }
}

live-demo: https://plnkr.co/edit/wugNC6S27FB48EtRN906?p=preview

Answer 2

Ng5-Dynamic Selectoption - , ,

template.html

//

<select (change)="countryChange($event)" >
  <option>Select</option>
  <option *ngFor="let c of countries" [ngValue]="c.country">{{ c.country }}</option>
</select>

<select (change)="statesChange($event)">
  <option>Select</option>
  <option *ngFor='let state of states' [ngValue]="state.name">{{ state.name }}</option>
</select>

<select >
  <option>Select</option>
  <option *ngFor='let city of cities' [ngValue]="city">{{ city }}</option>
</select>

component.ts

var = [{"": "", "": [{"": "", "": ["1", "2", "3"]}, {"": "", "": ["orc1", "oruc2", "oruc3"]}, {"name": "", "towns": ["3c1", "3c2", "3c3"] }]}, {"country": "Albania", "states": [{"name": "Korce", "towns": ["c1", "c2", "c3"]}, {"name": "Kukes", "towns": ["orc1", "oruc2", "oruc3"]}, {"name": "Lezhe", "towns": ["orc1", "oruc2", "oruc3"] }, {"name": "Shkoder", "towns": ["orc1", "oruc2", "oruc3"]}, {"name": "Tirane", "towns": ["orc1", "oruc2 "," oruc3 "]}]},
{"": "", "": []}
]

states= []; cities = [];
countryChange(e){
  console.log(e.target.value)
  this.countries.filter(element => {
    if(element.country == e.target.value){
      console.log(element.states[0],"first state")
      this.states = element.states;
    }
  });
  this.cities = []
}
statesChange(evt){
  console.log(evt.target.value,this.states)
  this.states.filter( element =>{
    if(element.name == evt.target.value){
      this.cities = element.cities;
    }
  })
}