Change dynamic textbox border color in Angular

Issue

I'm generating textboxes in angular

<span *ngFor="let list of lists[0].question; let i = index">
                    {{ list }}  
 <input type="text" *ngIf="i != lists[0].question.length-1" [(ngModel)]="values[i]"/>   
</span>

In this for loop textbox is being generated

i'm calling function on button click that get all the data from values variable

for (var i = 0; i < this.values.length; i++) {

   if(this.values[i]=='somevalue')
    {
     // change this particular textbox color
    }

 }

I want to change the textbox border color of that particular index only not with all the textboxes values. Any Solution Thanks

Solution

Well, if you want to change the color when you click a button you can use a variable (if only one of them can be change the color) or and array

Only one

indexAttention:number=-1;
checkValue(variable:string)
{
   //better than use a "typical for just use findIndex
   this.indexAttention=this.values.findIndex(x=>x==variable)
}

//and 
<input [style.border-color]="i==indexAttention?'red':null ...>

If you has more you can create an array with the index of the elements. For this we can use map

indexesAttention:number[]=[]
checkValue(variable:string)
{
   //map convert an array in another with the same elements and the values  calculates
   //in this case, if the value is equal to the variable
   //return the index, else return -1
   this.indexesAttention=this.values.map((x,index)=>x==variable?index:-1)
}

Then we write

<input [style.border-color]="indexesAttention.indexOf(i)>=0?'red':null ...>

NOTE: Is good know the differents methods to iterate in an array: find, findIndex,forEach,map... (Take a look to the mozilla page)

Update if we want to check severals words in a list it's better that our function return an array -not change the variable-

checkValue(variable:string):number[]
{
   return this.values
         .map((x,index)=>x==variable?index:-1)
         .filter(x=>x!=-1) //only want the index>>-1
}

So we can in click function

   click()
   {
         this.indexesAttention=[] //clean the array
         this.lists.forEach(x=>{   //iterate using forEach

                                   //concat two arrays
           this.indexesAttention=[...this.indexesAttention,
                                  ...this.checkValue(x)]
         })
   
   }

Now, we are using the spread operator to concat two arrays

NOTE: I know that there're many concepts but really, about arrays, there are no more

NOTE2: you can use also

<input 
[style.border-color]="lists.indexOf(values[i])>=0?'red':null"
...>

And you forget the functions

Answered By - Eliseo