There are places in any programming language that have surprises. For example, the
Null value in the C or C++ languages.
It is important to pay attention to detail when you write scripts. For example, strings must be enclosed in quotation marks.
Order of Script Interpretation
This behavior is specific to Internet Explorer. ASP and WSH have different execution models (as do other hosts).
Automatic Type Coercion
"100" == 100; false == 0;
To check that both the type and value are the same, use the strict equality operator (===). The following both evaluate to false:
"100" === 100; false === 0;
Operator precedence determines when an operation is performed during the evaluation of an expression. In the following example multiplication is performed before subtraction, even though the subtraction appears first in the expression.
theRadius = aPerimeterPoint - theCenterpoint * theCorrectionFactor;
Using for...in Loops with Objects
When you iterate through the properties of an object with a for...in loop, you cannot predict or control the order in which the fields of the object are assigned to the loop counter variable. Moreover, the order may be different in different implementations of the language.
The with statement is convenient for accessing properties that already exist in a specified object, but cannot be used to add properties to an object. To create new properties in an object, you must refer to the object specifically.
Although you use the
this keyword inside the definition of an object to refer to the object itself, you cannot use
this or similar keywords to refer to the currently executing function when that function is not an object definition. If the function is to be assigned to an object as a method, you can use the
this keyword within the function to refer to the object.
Writing a Script That Writes a Script in Internet Explorer
The </SCRIPT> tag terminates the current script if the interpreter encounters it. To display "</SCRIPT>" itself, rewrite this as at least two strings, for example, "</SCR" and "IPT>", which you can then concatenate together in the statement that writes them out.
Implicit Window References in Internet Explorer
Because more than one window can be open at a time, any implicit window reference points to the current window. For other windows, you must use an explicit reference.