Updating Elements in an Array Using JavaScript is Not Functioning as Expected

In my Angular application, I have included some lines of TypeScript code which involve Boolean variables in the constructor and an array of objects. Each object in this array contains input variables.

selftest: boolean;
failed: boolean;

    locoStateItems = [
    {
        name: 'FAILED',
        isSelected: this.failed
    },
    {
        name: 'SELFTESTED',
        isSelected: this.selftest
    }

When a different function is called later on:

toggleMe(name: string){
   if (name === 'FAILED') {
       this.failed = !this.failed
   } else if(name === 'SELFTESTED'){
       this.selftest = !this.selftest;
   }
}

The displayed locoStateItems in the DOM do not get updated automatically unless I explicitly assign values as follows:

locoStateItem[0].isSelected = this.failed;
locoStateItem[1].isSelected = this.selftest;

I am looking for an explanation for this behavior and suggestions on how to avoid it. Can someone help?

javascriptarraystypescriptobject

Answer №1

Boolean variables are primitive, so when you declare an array with boolean values, the values are simply assigned and not linked to the original variables. This means that changes to the variables do not automatically update in the array.

If you want the array objects to reflect the updated boolean values, you will need to manually update them as needed.

To achieve this functionality, consider modifying the function like so:

toggleMe(name: string){
   if (name === 'FAILED') {
       this.failed = !this.failed;
       this.locoStateItem[0].isSelected = this.failed;
   } 
   else if(name === 'SELFTESTED'){
       this.selftest = !this.selftest;
       this.locoStateItem[1].isSelected = this.selftest;
   }
}

Based on your question, this revised method should meet your requirements.

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