How to display multi dimensional array into the multiple dropdown menu? - angular5

Question

I am working in multiple dropdown menu. I have created an array from php and it looks like this:
https://api.myjson.com/bins/1emzic
Now from this json I want to display 4 dropdown menu.
In the first drop down I need to display
"FS A", "FS MT" and "FS OTHER"
Based on the first selection I need to display its related data in second third and fourth and so on as I add in my data.
This is what I need to bind
<select [(ngModel)]="first" id="first">
<option value="" disabled selected>select a category</option>
<option *ngFor="let item of first_list" [value]="item.category">{{item.category}}</option>
</select>
<br>
<select [(ngModel)]="second" id="second">
<option value="" disabled selected>select a category</option>
<option *ngFor="let item of first_list" [value]="item.category">{{item.category}}</option>
</select>
<br>
<select [(ngModel)]="third" id="third">
<option value="" disabled selected>select a category</option>
<option *ngFor="let item of first_list" [value]="item.category">{{item.category}}</option>
</select>
<br>
<select [(ngModel)]="four" id="four">
<option value="" disabled selected>select a category</option>
<option *ngFor="let item of first_list" [value]="item.category">{{item.category}}</option>
</select>
Here is my json data
{"FS A":{"BKK":{"BKK PULL":{"BKK SR1":[]},"BKK PUSH":{"BKK BCDE1":[],"BKK BAKE SE1":[]}},"RSM2":{"CHIANGMAI":{"CMI WS SE1":[],"CMI WS SE2":[]},"NORTH":{"NO1 SE1":[],"NO2 SEPLUS1":[],"NO3 SE1":[]},"ASM HOTEL BKK":{"BKK HO 5STARS1":[],"BKK HO SR1":[],"BKK HO SR2":[],"BKK HO SR3":[]}}},"FS MT":{"FSR1":{"FSA1":{"FS MAKRO":[]}},"FSR2":{"FSA2":{"FS FOODLAND":[],"FS GAS STATION":[],"FS VILLA MARKET JP":[],"SIAM FOODSERVICE":[]}},"FS LOCAL EXP":{"FS LOCAL EXP BKK":{"FS LOCAL EXP BKK":[]},"FS LOCAL EXP CD":{"FS LOCAL EXP CD":[]},"FS LOCAL EXP MM":{"FS LOCAL EXP MM":[]}}},"FS OTHER":{"FS OTHER":{"FS OTHER":{"FS OTHER":[]}}}}
Can anybody help me in this?
Here I am working:
https://stackblitz.com/edit/angular-dsylxi

Answer 1

You need to define the dependency on each other and based on that you can fill the models and its options. I will go for generic solution which can be applied with one function and works for all the drop-downs.
This are the model variables you need
wholeList:any = [];
first:any = [];
second:any = [];
third:any = [];
four:any = [];
firstModel = ''
secondModel = ''
thirdModel = ''
fourModel = ''
Then first you fill the first dropdown
this.testService.get_data().subscribe(
res => {
this.wholeList = res;
this.first = Object.keys(this.wholeList).map(a=> a);
console.log("res", this.first);
},
err => {
console.log(err);
}
)
Then in the view you need to fire a dependency which should look like this, note that I am defining dependency ChangeDropdown(this.wholeList[firstModel],'second')"
<select [(ngModel)]="firstModel" id="first" (ngModelChange)="ChangeDropdown(this.wholeList[firstModel],'second')">
<option value="" disabled selected>select a category</option>
<option *ngFor="let item of first" [value]="item">{{item}}</option>
</select>
<br>
<select [(ngModel)]="secondModel" id="second" (ngModelChange)="ChangeDropdown(this.wholeList[firstModel][secondModel],'third')">
<option value="" disabled selected>select a category</option>
<option *ngFor="let item of second" [value]="item">{{item}}</option>
</select>
<br>
<select [(ngModel)]="thirdModel" id="third" (ngModelChange)="ChangeDropdown(this.wholeList[firstModel][secondModel][thirdModel],'four')">
<option value="" disabled selected>select a category</option>
<option *ngFor="let item of third" [value]="item">{{item}}</option>
</select>
<br>
<select [(ngModel)]="fourModel" id="four">
<option value="" disabled selected>select a category</option>
<option *ngFor="let item of four" [value]="item">{{item}}</option>
</select>
and finally one common function which will update the models
ChangeDropdown = (value,dropdownName) =>{
this[dropdownName] = Object.keys(value).map(a=>{
return a;
})
}
Demo