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copied!<p><strong>UPD</strong> (from my comment): It is certainly not a good practice to pick some magic number to indicate value absence, unless you can be completely sure this magic number would not appear as a result of some arithmetics (which generally is true). So the best approach here is either to use a wider type than <code>int</code> (e.g. <code>Number</code>), or pass some flag (<code>Boolean</code> value) to function, as well as <code>int</code>, to indicate actual value absence. Choice should depend on whether you want to emphasize the importance of fact that passed value is integral.</p> <hr> <p>If you feel comfortable with expanding argument type, then you should use <code>NaN</code> and do this:</p> <pre><code>function setMyValue (myVar : Number = NaN) : void { if ( isNaN(myVar) ) { /* Generate a value for myVar */ } else { /* Use the supplied value for myVar */ } } </code></pre> <p>That is both more technically accurate and it is also more stable. It will also allow you to strongly type at compile-time and would not cause weird bugs as in case of using <code>Object</code>.</p> <p>Note that this will not work with <code>int</code> as one of the answers suggests. <code>int</code> has <em>only</em> numerical values, and <code>NaN</code> will get coerced to 0. You will need to use <code>Number</code> type. </p> <p>If you're worried about performance - don't be. Using <code>Number</code> instead of <code>int</code> or <code>uint</code> is generally OK.</p> <hr> <p><strong>UPD:</strong> If you want to explicitly mark that argument should be integral just use additional flag and exact type - it would be much clearer.</p> <pre><code>function setMyValue (isIntValueSupplied : Boolean = false, intValue : int = 0) : void { if ( isIntValueSupplied ) { /* Generate or use a default value of intValue */ } else { /* Use the supplied value for intValue */ } } </code></pre> <hr> <p>Another option is to define your own type with additional value, e.g. <code>MaybeInt</code>, which holds integer value and a flag (whether it was actually initialized or not). That way you would clearly signal that value should be integral or <em>no-value</em>. However, this approach may be a bit bulky.</p>

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