typeof

<h2 id="examples">Examples</h2>
<h3>C#</h3><p>
In <a href="/facts/C_Sharp_(programming_language)/UC2gxeyb">C#</a>:</p>// Given an object, returns if it is an integer.
// The "is" operator can be also used to determine this.
public static bool IsInteger(object o)
{
    return o.GetType() == typeof(int);
}

<h3>C</h3>
<p>As of <a href="/facts/C23_(C_standard_revision)/1VvQNwSb">C23</a> typeof is a part of the C standard. The operator typeof_unqual was also added which is the same as typeof, except it removes cvr-qualification and atomic qualification.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a><a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a>
</p><p>
In a non-standard (GNU) extension of the <a href="/facts/C_(programming_language)/Ky2No763">C programming language</a>, typeof may be used to define a general macro for determining the maximum value of two parameters:</p>#define max(a,b) ({ typeof (a) _a = (a); typeof (b) _b = (b); _a > _b ? _a : _b; })

<h3>Java</h3>
<p>Java does not have a keyword equivalent to typeof. All objects can use Object's getClass() method to return their class, which is always an instance of the Class class. All types can be explicitly named by appending ".class", even if they are not considered classes, for example int.class and String[].class . There is also the instanceof operator for <a href="/facts/Type_introspection/c0tKqdYB">type introspection</a> which takes an instance and a class name, and returns true for all subclasses of the given class.
</p>
<h3>JavaScript</h3><p>
In <a href="/facts/JavaScript/XhhIIEsl">JavaScript</a>:</p>function isNumber(n)
{
  return ( typeof n === 'number' );
}

<h3>TypeScript</h3>
<p>In <a href="/facts/TypeScript/W9J27V1N">TypeScript</a>:<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a>
</p>
function (param: typeof existingObject) { ... }

let newObject: typeof existingObject;

<h3>VB.NET</h3>
<p>In <a href="/facts/VB.NET/09mPEo4q">VB.NET</a>, the C# variant of "typeof" should be translated into the VB.NET's <i>GetType</i> method. The TypeOf keyword in VB.NET is used to compare an object reference variable to a data type.
</p><p>
The following example uses TypeOf...Is expressions to test the type compatibility of two object reference variables with various data types.</p>Dim refInteger As Object = 2

MsgBox("TypeOf Object[Integer] Is Integer? " & TypeOf refInteger Is Integer)
MsgBox("TypeOf Object[Integer] Is Double? " & TypeOf refInteger Is Double)

Dim refForm As Object = New System.Windows.Forms.Form

MsgBox("TypeOf Object[Form] Is Form? " & TypeOf refForm Is System.Windows.Forms.Form)
MsgBox("TypeOf Object[Form] Is Label? " & TypeOf refForm Is System.Windows.Forms.Label)
MsgBox("TypeOf Object[Form] Is Control? " & TypeOf refForm Is System.Windows.Forms.Control)
MsgBox("TypeOf Object[Form] Is IComponent? " & TypeOf refForm Is System.ComponentModel.IComponent)

<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Sizeof/f7x8ttfX">sizeof</a></li>
<li><a href="/facts/Decltype/PnAAQ1Co">decltype</a></li>
<li><a href="/facts/Type_introspection/c0tKqdYB">Type introspection</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>"TypeOf Operator (Visual Basic)". MSDN. Archived from the original on Nov 28, 2016. <a href="https://web.archive.org/web/20161128133108/https://msdn.microsoft.com/en-us/library/0ec5kw18(VS.80).aspx" target="_blank">https://web.archive.org/web/20161128133108/https://msdn.microsoft.com/en-us/library/0ec5kw18(VS.80).aspx</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>"typeof (C#)". MSDN. Archived from the original on Sep 10, 2016. <a href="https://web.archive.org/web/20160910105030/https://msdn.microsoft.com/en-us/library/58918ffs(VS.80).aspx" target="_blank">https://web.archive.org/web/20160910105030/https://msdn.microsoft.com/en-us/library/58918ffs(VS.80).aspx</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>"Declarations - D Programming Language 1.0". Digital Mars. Dec 30, 2012. Archived from the original on Oct 7, 2023. <a href="http://digitalmars.com/d/1.0/declaration.html#Typeof" target="_blank">http://digitalmars.com/d/1.0/declaration.html#Typeof</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>"Typeof" in "Using the GNU Compiler Collection". <a href="https://gcc.gnu.org/onlinedocs/gcc/Typeof.html" target="_blank">https://gcc.gnu.org/onlinedocs/gcc/Typeof.html</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>Meneide, JeanHeyd (2021-03-07). "Not-So-Magic - typeof(…) in C | r2". Open Standards. Retrieved 2021-12-02. <a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2685.htm" target="_blank">http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2685.htm</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>"N2927: Not-so-magic - typeof for C". Open Standards. 2022-02-02. Archived from the original on Dec 1, 2023. <a href="https://open-std.org/JTC1/SC22/WG14/www/docs/n2927.htm" target="_blank">https://open-std.org/JTC1/SC22/WG14/www/docs/n2927.htm</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
<li id="fn:7"><p>"Consider renaming remove_quals" (PDF). Open Standards. 2022-02-06. Archived (PDF) from the original on Feb 17, 2024. <a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2930.pdf" target="_blank">https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2930.pdf</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li>
<li id="fn:8"><p>"Using 'typeof' to infer a type". Learn TypeScript. Retrieved 2022-01-28. <a href="https://learntypescript.dev/08/l4-typeof-infer/" target="_blank">https://learntypescript.dev/08/l4-typeof-infer/</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li>
</ol>

typeof open-in-new

typeof