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You can use the typeof()
operator to examine an "operand" (a string, variable, method,
function, keyword, object, or property). typeof
is an unusual operator because it is not represented by punctuation
characters but instead by the typeof
keyword. It is a unary operator that is placed before a single operand,
which can of any type. The typeof()
operator will return a string that describes the type of operand. In
other words, the typeof()
operator will tell you what sort of string, variable, method, function,
keyword, object, or property you have. This might
be useful if want to carry out the operation (so you can select the
appropriate operation depending on the type of the operand).
typeof
syntax can take one of two forms:
-- OR --
<SCRIPT>
var sSize = "big";
var nSize = 1;
var todayDate = new Date();
</SCRIPT>
<BODY>
<SCRIPT>
document.write("sSize =
" + typeof(sSize) + "
<BR>")
document.write("nSize = "
+ typeof(nSize) + "
<BR>")
document.write("todayDate =
" + typeof(todayDate) + "
<BR>")
document.write("nothingAtAll =
" + typeof(nothingAtAll) +
" <BR>")
document.write("null = " +
typeof(null) + "
<BR>")
document.write("false = "
+ typeof(false) + "
<BR>")
document.write("true = " +
typeof(true) + "
<BR>")
document.write("666 = " + typeof(666)
+ " <BR>")
document.write("A little bit of
text = " + typeof('A little bit
of text') + " <BR>")
document.write("document.linkColor
= " + typeof(document.linkColor)
+ " <BR>")
document.write("document.lastModified
= " + typeof(document.lastModified)
+ " <BR>")
document.write("document.anchors
= " + typeof(document.anchors)
+ " <BR>")
document.write("window.history
= " + typeof(window.history)
+ " <BR>")
document.write("window.length =
" + typeof(window.length)
+ " <BR>")
document.write("Math.E = "
+ typeof(Math.E)
+ " <BR>")
document.write("blur = " +
typeof(blur) + "
<BR>")
document.write("Date = " +
typeof(Date) + "
<BR>")
document.write("String = "
+ typeof(String) + "
<BR>")
</SCRIPT> |
