Q:

primeng - Select only one checkbox item at a time

Is it possible to configure the primeng's checkbox module to behave as a selectbox, e.g. user can select only one checkbox at a time? 
My component:
<div class="ui-g" style="width:250px;margin-bottom:10px">
    <div class="ui-g-12"><p-checkbox name="group1" value="New York" label="New York" [(ngModel)]="selectedCities" inputId="ny"></p-checkbox></div>
    <div class="ui-g-12"><p-checkbox name="group1" value="San Francisco" label="San Francisco" [(ngModel)]="selectedCities" inputId="sf"></p-checkbox></div>
    <div class="ui-g-12"><p-checkbox name="group1" value="Los Angeles" label="Los Angeles" [(ngModel)]="selectedCities" inputId="la"></p-checkbox></div>
</div>

Working stackblitz example. 

A:

I would suggest, that if you want a component that behaves like selectbox, use primeng's RadioButton component.  On the other hand you can change the behavior of your chceckbox as well:

You need use the onChange() event on every checkbox component to
know when user clicks on your checkbox. 
After the user clicks to a checkbox, you need to store the current element.  In your case it is the const latestCity = this.selectedCities[this.selectedCities.length - 1];.  Since the checkbox items are stored as string values in an array, the current selected item is the last element of that array. 
Lastly you need to empty the array and push the last selected item into that empty array:
this.selectedCities.length = 0;
this.selectedCities.push(latestCity);

Edited stackblitz.