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<1>IsArray functionReturns the Boolean value to indicate whether a variable is an array.
grammar
IsArray(varname)
The varname parameter can be any variable.
illustrate
If the variable is an array, the IsArray function returns True; otherwise, the function returns False. Using the IsArray function is effective when an array is contained in a variable.
<2>IsDate function
Returns a Boolean value to indicate whether an expression can be converted to a date.
grammar
IsDate(expression)
The expression parameter can be any date expression or string expression that can be recognized as a date and time.
illustrate
If the expression is a date or can be legally converted to a valid date, the IsDate function returns True; otherwise the function returns False. In Microsoft Windows operating systems, the valid date range is from January 1, 100 AD to December 31, 9999 AD; the legal date range varies according to the operating system.
<3>IsEmpty function
Returns the Boolean value to indicate whether the variable has been initialized.
grammar
IsEmpty(expression)
The expression parameter can be any expression. However, since IsEmpty is used to determine whether a variable has been initialized, the expression parameter is often a variable name.
illustrate
If the variable is not initialized or explicitly set to Empty, the function IsEmpty returns True; otherwise the function returns False. If expression contains more than one variable, False will always be returned.
<4>IsNull function
Returns a Boolean value indicating whether the expression does not contain any valid data (Null).
grammar
IsNull(expression)
The expression parameter can be any expression.
illustrate
If expression is Null, IsNull returns True, that is, the expression does not contain valid data, otherwise IsNull returns False. If expression consists of multiple variables, Null in any constituent variable of the expression will return True to the entire expression.
The Null value indicates that the variable does not contain valid data. Null is different from Empty, which states that the variable is not initialized. Null is also different from zero-length string(), which often refers to empty strings.
Focus on using the IsNull function to determine whether an expression contains a Null value. In some cases, you want to take the expression value True, such as IfVar=Null and IfVar<>Null, but they are usually always False. This is because any expression containing Null is Null itself, so the result of the expression is False.
<5>IsNumeric function
Returns the Boolean value to indicate whether the value of the expression is a number.
grammar
IsNumeric(expression)
The expression parameter can be any expression.
illustrate
If the entire expression is recognized as a number, the IsNumeric function returns True; otherwise the function returns False.
If expression is a date expression, the IsNumeric function returns False.
<6>IsObject function
Returns a Boolean value to indicate whether the expression refers to a valid Automation object.
grammar
IsObject(expression)
The expression parameter can be any expression.
illustrate
IsObject returns True if expression is an Object subtype variable or a user-defined object; otherwise the function returns False.
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