CODEWITHSUNDEEP
javascriptregex
Dust_In_The_Wind
Dust_In_The_Wind

Reputation: 3692

JavaScript Regex unexpected behavior with .test()

I am creating a Regular Expression in JavaScript which should look for both numbers (at least 1) and letters (at least 1), with the total length being between 6 and 10. I came across some unexpected behavior.

My regex - /^[a-z+\d+]{6,10}$/g.

This doesn't work properly because being in a character class, it checks for letters or numbers, but noth BOTH. Therefore, I would expect "123456" to fail, because while it contains 6 characters, and has at least 1 digit, it does not include 1 letter.

However, in the below code snippet, when I store the regex in the rgx variable and use .test() on it, it somehow correctly returns false, as shown in the second console.log statement. But on the very next line when I directly use the regex with .test(), it returns true. 

let rgx = /^[a-z+\d+]{6,10}$/g;

// works fine
console.log(rgx.test("abcd12"));

// returns false
console.log(rgx.test("123456"));

// same regex returns true
console.log(/^[a-z+\d+]{6,10}$/g.test("123456"));

What's going on here?

Upvotes: 0

Views: 192

Answers (2)

Hasanuzzaman Rana
Hasanuzzaman Rana

Reputation: 123

try this instead /^[^a-z0-9]{6,10}$/g

Upvotes: -1

mickl
mickl

Reputation: 49945

Try

let rgx = /^[a-z+\d+]{6,10}$/g;
let rgx2 = /^[a-z+\d+]{6,10}$/g;
console.log(rgx.test("abcd12")); //true
console.log(rgx2.test("123456")); //true

It's because

Javascript RegExp object is stateful i.e. if you re-use a RegExp object (with 'g' flag set), subsequent matches would start from the end of the last match.

Upvotes: 4

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