r">width</span> * <span class="tm-vr">obj</span>.<span class="tm-vr">heigth</span>;<a class="playground-link" href="https://www.typescriptlang.org/play/#src=const%20obj%20%3D%20%7B%20width%3A%2010%2C%20height%3A%2015%20%7D%3B%0A%2F%2F%20Why%20is%20this%20NaN%3F%20Spelling%20is%20hard!%0Aconst%20area%20%3D%20obj.width%20*%20obj.heigth%3B">Try</a></pre></p>
<p>Other programming languages would usually cause these programs to either fail to start at all, or terminate the program mid-execution, if these sorts o