Semantic-Org/Semantic-UI · warning

{name} is not formatted correctly

Error message

{name} is not formatted correctly

What it means

Default prompt for the Semantic UI Form `regExp` rule (settings.rules.regExp, form.js:1357). Shown when a field's value does not match a caller-supplied regular expression. The rule accepts either a RegExp object or a string (with optional `/pattern/flags` syntax parsed via `settings.regExp.flags`, form.js:1362-1376) passed as the bracketed ancillary value or `rule.value`.

Source

Thrown at src/definitions/behaviors/form.js:1258

    email   : /^[a-z0-9!#$%&'*+\/=?^_`{|}~.-]+@[a-z0-9]([a-z0-9-]*[a-z0-9])?(\.[a-z0-9]([a-z0-9-]*[a-z0-9])?)*$/i,
    escape  : /[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g,
    flags   : /^\/(.*)\/(.*)?/,
    integer : /^\-?\d+$/,
    number  : /^\-?\d*(\.\d+)?$/,
    url     : /(https?:\/\/(?:www\.|(?!www))[^\s\.]+\.[^\s]{2,}|www\.[^\s]+\.[^\s]{2,})/i
  },

  text: {
    unspecifiedRule  : 'Please enter a valid value',
    unspecifiedField : 'This field'
  },

  prompt: {
    empty                : '{name} must have a value',
    checked              : '{name} must be checked',
    email                : '{name} must be a valid e-mail',
    url                  : '{name} must be a valid url',
    regExp               : '{name} is not formatted correctly',
    integer              : '{name} must be an integer',
    decimal              : '{name} must be a decimal number',
    number               : '{name} must be set to a number',
    is                   : '{name} must be "{ruleValue}"',
    isExactly            : '{name} must be exactly "{ruleValue}"',
    not                  : '{name} cannot be set to "{ruleValue}"',
    notExactly           : '{name} cannot be set to exactly "{ruleValue}"',
    contain              : '{name} must contain "{ruleValue}"',
    containExactly       : '{name} must contain exactly "{ruleValue}"',
    doesntContain        : '{name} cannot contain  "{ruleValue}"',
    doesntContainExactly : '{name} cannot contain exactly "{ruleValue}"',
    minLength            : '{name} must be at least {ruleValue} characters',
    length               : '{name} must be at least {ruleValue} characters',
    exactLength          : '{name} must be exactly {ruleValue} characters',
    maxLength            : '{name} cannot be longer than {ruleValue} characters',
    match                : '{name} must match {ruleValue} field',
    different            : '{name} must have a different value than {ruleValue} field',
    creditCard           : '{name} must be a valid credit card number',

View on GitHub (pinned to 597843ab84)

Solutions

1. Verify the regex against the intended input in a regex console first.
2. Pass the pattern as a real RegExp object via `rule.value` to avoid `/.../ ` parsing edge cases.
3. Escape brackets inside the pattern or use `rule.value` when the pattern itself contains `[`/`].`
4. Add a custom `prompt` so the failure is actionable, e.g. `'Use 3 uppercase letters'`.

Example fix

// before - bracket parser confused by inner brackets / unanchored
rules: [{ type: 'regExp[/[A-Z]{3}/]' }]

// after - pass RegExp object + clear prompt
rules: [{ type: 'regExp', value: /^[A-Z]{3}$/, prompt: 'Code must be 3 uppercase letters' }]

const pattern = /^[A-Z]{3}$/; // your rule
if (!pattern.test($field.val())) { /* show inline guidance */ }

const isRegExpRule = (r) => r && (r.value instanceof RegExp || typeof r.type === 'string' && /\[.*\]/.test(r.type));

When it happens

Trigger: Field rule `{type:'regExp[/^[A-Z]{3}$/]'}` with input `ab` or `abcd`; or `{type:'regExp', value:/\d{4}/}` with input `abc`. Any value for which `value.match(regExp)` is falsy triggers the prompt.

Common situations: Typo in the bracket-delimited regex (unescaped `]`, missing flags), passing a string regex with `/` delimiters inconsistently, or a regex that does not anchor and unexpectedly matches/fails. Also: forgetting that an empty value still runs the rule (use `empty`/`optional` first).

Related errors

• {name} must be a valid url
• {name} must be an integer
• {name} must be a decimal number
• {name} must be set to a number
• {name} must be "{ruleValue}"

AI-assisted analysis of Semantic-Org/Semantic-UI@597843ab84 (2026-08-13). Data as JSON: /api/errors/d650334a8173b4b4. Report an issue: GitHub.