Semantic-Org/Semantic-UI · warning

{name} must be set to a number

Error message

{name} must be set to a number

What it means

Default prompt for the Semantic UI Form `number` rule (settings.rules.number, form.js:1417). It tests against `settings.regExp.number` = `/^-?\d*(\.\d+)?$/` (form.js:1244). Quirk: the regex matches an empty string `''` and a lone `-`, so those pass validation — pair with an `empty` rule when the field is required.

Source

Thrown at src/definitions/behaviors/form.js:1261

    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',
    minCount             : '{name} must have at least {ruleValue} choices',
    exactCount           : '{name} must have exactly {ruleValue} choices',
    maxCount             : '{name} must have {ruleValue} or less choices'

View on GitHub (pinned to 597843ab84)

Solutions

1. Add `empty` as a separate rule if the field is required: `rules:[{type:'empty'},{type:'number'}]`.
2. Strip grouping separators / replace comma decimals before validation.
3. Use `integer` or `decimal` when a more specific numeric type is intended.
4. Provide a custom `prompt`.

Example fix

// before - blank input passes the number regex
rules: [{ type: 'number' }]

// after - require presence + numeric
rules: [
  { type: 'empty', prompt: 'Amount is required' },
  { type: 'number', prompt: 'Amount must be a number' }
]

const v = $field.val();
const isNumber = /^-?\d*(\.\d+)?$/.test(v);
const isRequiredAndBlank = (v === '' || v === '-'); // these PASS the built-in rule!
if (!isNumber || isRequiredAndBlank) { /* warn */ }

const isStrictNumber = (v) => v !== '' && v !== '-' && /^-?\d*(\.\d+)?$/.test(String(v));

When it happens

Trigger: `{type:'number'}` with input `1.2.3`, `abc`, `--4`, or `3,14` (comma). Empty input or `-` alone do NOT trigger it (they pass).

Common situations: Required numeric fields left blank still passing because the regex matches `''`; localized comma decimals; multiple dots in pasted data.

Related errors

• {name} must be a decimal number
• {name} must be a valid url
• {name} is not formatted correctly
• {name} must be an integer
• {name} must be "{ruleValue}"

AI-assisted analysis of Semantic-Org/Semantic-UI@597843ab84 (2026-08-13). Data as JSON: /api/errors/fd044d7593efaa95. Report an issue: GitHub.