error display in js
<p>guys im typing a piece of java script code which is surely wrong,but im not receiving any error message which i should receive,can you please explain why error message is not shown to me?</p>

<p>js code is </p>

<pre><code>document.write("num.toExponential() is " + num.toExponential()); 

alert("num.toExponential(4) is " + num.toExponential(4)); //displays 7.7123e+1

alert("num.toExponential(2) is " + num.toExponential(2)); //displays 7.71e+1

alert("77.1234.toExponential() is " + 77.1234.toExponential()); //displays 7.71234e+1

alert("77 .toExponential() is " + 77 .toExponential()); //displays 7.
</code></pre>

<p>this should display an error which it is not showing,
also output is not shown to me so there is error which itself isnt shown to me,
what should i do to see that error ?
if i change value of num to some number it works properly and shows me output . </p>
