left-aligns the string within the string variable. Any remaining positions in the string variable are replaced by spaces. If the string is longer than the string variable, only the leftmost characters up to the length of the string variable are copied. With the
左对齐字符串变量中的字符串，字符串变量中剩余的位置用空格代替。如果字符串变量的长度小于字符串的长度，则仅复制字符串中前 n 个字符，n 由字符串变量的长度决定。