Stringlengthcheck: put excess of characters in a input box should support and make sure it is not taking that.
字符串长度检查：在输入框输入超出长度的字符串将会被允许，但要确保它不被程序通过。
2
First, I'm going to do a sanity check strlen so we've used stringlength, strlen, before.
首先，我先做一个检查，我们以前使用过字符串长度函数。
3
In addition to comparing the length and index values for equality, you must also check for either a null Number after parsing or an empty input string (" "or length of zero).