Learn TypeScript 3 by Building Web Applications

Isolating the utility function

A small detail that we have left aside is the isEnter function. To have cleaner code, we can isolate it in a class and define it as a static member:

class EventUtils { 
    static isEnter(event: KeyboardEvent): boolean { 
        let isEnterResult = false; 

        if(event !== undefined && event.defaultPrevented) { 
            return false; 
        } 

        if (event == undefined) { 
            isEnterResult = false; 
        } else if (event.key !== undefined) { 
            isEnterResult = event.key === 'Enter'; 
        } else if (event.keyCode !== undefined) { 
            isEnterResult = event.keyCode === 13; 
        } 

        return isEnterResult; 
    } 
} 

We can invoke it as easily as before, using EventUtils.isEnter(...​). This doesn't change much, but is cleaner and conveys more meaning. One important rule, whenever you develop ...