If the character is an operand, append it to the result string.
如果字符是操作数，将它添加到结果字符串。
2
In particular, if one operand is a string and the other a number, the string will be converted to a number and the two operands then compared numerically. This can lead to subtle errors.
The string format operation involves the processing of the FormatString, looking for format specification sequences, and using these sequences to format the associated data from the right operand.