Angular 2 ng-class取决于功能

Question

Im trying to change the class of some elements based on an array. I have declared a function to return a boolean and say if the string(state/class) is contained in the array. I have call it isState(st: string) {return (this.ArrayWithClasses.indexOf(st) > 0)}

And then I do

[ngClass]="{'class-I-Want-To-Activate': isState('evaluating-this-state') }"

But it is´t working. You see my mistake? A best solution?

Edit: It is working if I use just a boolean to toggle the class. So I consider if function is what is wrong...

Answer 1

Use the below

isState(st: string) {
    let temp=this.ArrayWithClasses.indexOf(st)
    if(temp)
        return true;
    else
        return false;
}

Answer 2

You shouldn't check if indexOf() value is > 0 , because, if that string is located on the first place in array, you will get 0.

isState(st: string) {
    let temp = this.ArrayWithClasses.indexOf(st);
    if(temp != -1)
        return true;
    else
        return false;
}

If searched string is not located in the array , you will get -1 value for that.