Check if a string is an octal number

Test for octal digits with an optional 0o prefix.

JavaScript Version 1.0.0 · MIT · .md

function isOctal(text) { return /^(0o)?[0-7]+$/i.test(text); }

Input & expected output

"0o755"

true

The edge case

"789"

false

Know the limits

• Legacy leading-zero octal such as 0755 passes as plain digits.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Check whether all values are equal — Compare every item with the first using Object.is.
• Check whether an object is empty — Check for own enumerable string keys on a JSON object.
• Check whether an integer is even — Test parity for safe integers, including zero and negative values.