Question

I have a string which is of format ABC1234567

var value = "ABC1234567"  
var first3Letters = value.substring(0,3);  // ABC   
var next7Letters = value.substring(3,7);   //1234567`

Now I want to validate whether variable first3Letters contains only alphabets, and variable next7letters contains only integers.

How do I do this?

Answer 1

Here’s one way:

if ( /^[a-z]+$/i.test (first3Letters ) ) {
    // It's good.
}

if ( /^\d+$/.test (next7Letters) ) {
    // It's good.
}

See it in action at jsFiddle.

---

Regex explained:

1. ^ specifies the beginning of the string.
2. & specifies the end of the string.
3. [a-z] is any word character (A, B, C, etc., but NOT numbers or the the underscore — which \w would allow).
4. \d is any number character (0, 1, 2, etc.)
5. + means one or more of the previous.
6. The i at the end (i.test) tells JS to run a case-insensitive search.

So the regexes are essentially saying, “From the beginning to the end, are there nothing but 1 or more (word or number) characters.”

See also: Regular expressions tutorial.