regex not repeating dot character javascript

Question

I have come up my regex in javascript ^[a-zA-Z0-9.]+([.][a-zA-Z0-9]+)$ which I am trying to filter out string.

• No dot character at the begin nor end
• dot character can be middle of other Alphabet letter or numbers
• If dot character cannot be appear more than twice

These are my expected pass cases

• foo.bar
• f.o.o
• foo.bar.foo
• fo.123.321

These are my expected No-pass cases

• .foo
• .foo.
• foo.
• foo..bar
• .foo.bar

I feel like I am very close(or not at all). How can I filter out dot repeating dot characters? Thanks in advance!

Answer 1

I think that's what you looking for:

/^([a-zA-Z0-9]+\.)+([a-zA-Z0-9]+)$/

Tests

expected pass cases

/^([a-zA-Z0-9]+\.)+([a-zA-Z0-9]+)$/.test('foo.bar') // true
/^([a-zA-Z0-9]+\.)+([a-zA-Z0-9]+)$/.test('f.o.o') // true
/^([a-zA-Z0-9]+\.)+([a-zA-Z0-9]+)$/.test('foo.bar.foo') // true
/^([a-zA-Z0-9]+\.)+([a-zA-Z0-9]+)$/.test('fo.123.321') // true

Expected No-pass cases

/^([a-zA-Z0-9]+\.)+([a-zA-Z0-9]+)$/.test('.foo') // false
/^([a-zA-Z0-9]+\.)+([a-zA-Z0-9]+)$/.test('.foo.') // false
/^([a-zA-Z0-9]+\.)+([a-zA-Z0-9]+)$/.test('foo.') // false
/^([a-zA-Z0-9]+\.)+([a-zA-Z0-9]+)$/.test('foo..bar') // false
/^([a-zA-Z0-9]+\.)+([a-zA-Z0-9]+)$/.test('.foo.bar') // false