JavaScript fun: is a string composed of letters or numbers?

Sometimes you need to verify whether an input string is composed of letters or numbers. An English word exactly interprets this requirement-alphanumeric. Sometimes you need to verify whether an input string is composed of letters or numbers. An English word exactly interprets this requirement-alphanumeric.

Further refine this requirement:

1. The string consists of at least one character (that is, the Null String is not passed)

2. uppercase/lowercase English letters and 0-9 digits are allowed (this is the main character)

3. Other characters, as long as they appear, cannot exceed, such as spaces and underscores.

For this question, regular expressions are just a single sentence, but what if regular expressions are not used?

It is also very simple. You can use ASCII codes to traverse strings one by one to determine.

Let's take a look at the ASCII code range:

1. digit characters 48-57

2. uppercase letters 65-90

3. lowercase letter 97-122

All the characters in these ranges are valid characters, so those out of the range must be invalid characters.

But don't forget the special case mentioned above-a null string.

Well, with these materials, we can easily write them out.

Function alphanumeric (string) {if (string. length <1) {return false ;}for (var I = 0; I

 
  
57 & code <65 | code> 90 & code <97 | code> 122) {return false ;}} return true ;}

 

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