Check if a string contains only ASCII characters

Test that every character is in the 0–127 range.

JavaScript Version 1.0.0 · MIT · .md

function isAscii(text) { return /^[\x00-\x7F]+$/.test(text); }

Input & expected output

"[email protected]"

true

The edge case

"ana@bücher.example"

false

Know the limits

• The empty string fails.
• Oveyon refuses non-ASCII addresses with address_not_ascii; convert an international domain to punycode first (see the email collection).

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.