User Guide

The C-level API 357
char *JS_ValueToString()
Description
This function extracts a function argument from a jsval structure, converts it to a string, if
possible, and passes the converted value back to the caller.
Note: Do not modify the returned buffer pointer or you might corrupt the data structures of the
JavaScript interpreter. To change the string, you must copy the characters into another buffer and
create a new JavaScript string.
Arguments
JSContext *cx
, jsval v, unsigned int *pLength
• The cx argument is the opaque JSContext pointer that passes to the JavaScript function.
• The v argument is the jsval structure from which the string is to be extracted.
• The pLength argument is a pointer to an unsigned integer. This function sets *plength equal
to the length of the string in bytes.
Returns
A pointer that points to a null-terminated string if successful or to a null value on failure. The
calling routine must not free this string when it finishes.
JSBool JS_ValueToInteger()
Description
This function extracts a function argument from a jsval structure, converts it to an integer (if
possible), and passes the converted value back to the caller.
Arguments
JSContext *cx
, jsval v, long *lp
• The cx argument is the opaque JSContext pointer that passes to the JavaScript function.
• The v argument is the jsval structure from which the integer is to be extracted.
• The lp argument is a pointer to a 4-byte integer. This function stores the converted value
in
*lp.
Returns
A Boolean value: JS_TRUE indicates success; JS_FALSE indicates failure.