Returns the substring of the first argument string that precedes the first occurrence of the second argument string in the first argument string, or the empty string if the first argument string does not contain the second argument string.
If an argument is not of type string, it is first converted to a string using the string() function and then the result of that conversion is evaluated.
String conversions for node sets that are passed as arguments to this function may yield unexpected results. For more information, see string Function.
This function is case-sensitive.