1.0.4 • Public • Published

    MIT license npm version


    A simplified rewrite of the React PropTypes library, designed for use outside of React on arbitrary Javascript data.

    This can be used as a quick and simple data validation tool—for example, to validate config files, or data passed by a user into a function.


    To validate an object:

    const { validateProps, PropTypes } = require('prop-validator')
    const propTypes = {
      foo: PropTypes.string,
      bar: PropTypes.number,
      baz: PropTypes.oneOfType([PropTypes.string, PropTypes.number])
    const props = {
      foo: 'something',
      bar: 1234,
      baz: 'something else'
    const { results, errors, isValid } = validateProps(propTypes, props)
    console.log(isValid) // true
    console.log(results) // see below

    The results array will contain the following feedback:

        isValid: true,
        isRequired: false,
        valueType: 'string',
        valueExpectedType: 'string | null',
        valueExpectedTypeList: [ 'string', 'null' ],
        objectPath: 'foo',
        objectPathList: [ 'foo' ],
        key: 'foo',
        value: 'something',
        message: null,
        exception: null
        isValid: true,
        isRequired: false,
        valueType: 'number',
        valueExpectedType: 'number | null',
        valueExpectedTypeList: [ 'number', 'null' ],
        objectPath: 'bar',
        objectPathList: [ 'bar' ],
        key: 'bar',
        value: 1234,
        message: null,
        exception: null
        isValid: true,
        isRequired: false,
        valueType: 'string',
        valueExpectedType: 'string | number | null',
        valueExpectedTypeList: [ 'string', 'number', 'null' ],
        objectPath: 'baz',
        objectPathList: [ 'baz' ],
        key: 'baz',
        value: 'something else',
        message: null,
        exception: null

    Running the validator returns an object of two arrays: results and errors, and a boolean isValid. The former contains the validation results of all props, and the latter contains only any errors. If any errors were found, isValid will be false.

    If a given prop is invalid, like if we instead set bar to "1234" instead of a string in the previous example, the given error message will be the following:

    "Property 'bar' should be type 'number | null', but type 'string' was found"

    As can be seen from the contents of the results array, all checks are permitted to have a null value as well (which can also be undefined). If a value must be present and be a given type, the .isRequired type can be referenced instead, e.g. PropTypes.string.isRequired.

    Nested type checking

    Nested properties can be checked through the use of PropTypes.shape():

    const propTypes = {
      options: PropTypes.shape({
        name: PropTypes.string,
        age: PropTypes.integer,
        job: PropTypes.shape({
          title: PropTypes.string,
          tags: PropTypes.arrayOf(PropTypes.string)
    const props = {
      options: {
        name: 'Alice',
        age: 500,
        job: {
          title: 'CEO of Self-employed',
          tags: ['nothing', 'particularly', 'interesting']

    All validation results, including the nested ones inside of a PropTypes.shape() object, are returned in the results and errors flat arrays.

    Note that extra values are permitted inside of a shape object: it only checks whether all values that exist pass validation. If you must be sure that only the expected values are present and no others, the PropTypes.exact() validator can be used instead.

    Available type checkers

    Name Matches
    string Any string
    number Any number
    numberRange(min, max) Number in the range min ≤ n ≤ max, or another range type; see below
    integer Number that passes Number.isInteger()
    integerRange(min, max) Number that passes Number.isInteger() and is in a given range; see below
    boolean Any boolean (note: aliased as bool)
    function Any function (note: aliased as func)
    object Any plain object
    symbol Any symbol
    array Any array
    regex Any regular expression
    error Any error instance
    any Any defined value*
    null Only null
    undefined Only undefined**
    stringMatching(/regex/) String that matches a given regular expression
    oneOf([...values]) Value that matches a given literal
    oneOfType([...propTypes]) Value that matches a given propType
    arrayOf(propType) Array containing only members of a given propType
    objectOf(propType) Plain object containing only values of a given propType
    instanceOf(classObject) Instance of a given class
    customProp(func, type) Value that passes the given validator function (type is for output)
    shape({...propTypes}) Plain object whose values pass a given propTypes object
    exact({...propTypes}) Plain object whose values pass a given propTypes object and which is not allowed to have extra values

    *: any still requires a value to be set when .isRequired is used, so it does not validate undefined in that case.

    **: undefined still accepts the null value if .isRequired is not used.

    The error validator applies to any instance of an Error class or one that extends it (including TypeError, RangeError, etc).

    Number range checkers

    The numberRange type checker has several different subtypes:

    const propTypes = {
      rangeA: PropTypes.numberRange(0, 5),                  // 0 ≤ n ≤ 5
      rangeB: PropTypes.numberRange.inclusive(0, 5),        // 0 ≤ n ≤ 5; alias for .numberRange
      rangeC: PropTypes.numberRange.exclusive(0, 5),        // 0 < n < 5
      rangeD: PropTypes.numberRange.greaterThan(5),         // n > 5
      rangeE: PropTypes.numberRange.greaterThanOrEqual(5),  // n ≥ 5
      rangeF: PropTypes.numberRange.lessThan(5),            // n < 5
      rangeG: PropTypes.numberRange.lessThanOrEqual(5)      // n ≤ 5

    Additionally, the integerRange type checker does the exact same thing, except it also verifies if the given value is an integer.

    Differences with the original PropTypes library

    The API is similar to the original PropTypes library, but there are a few small changes. Since this is not designed for React or DOM objects, the following types are not supported: node, element, elementType.

    Conversely, this library contains the following validators that the original does not have: numberRange(), integer, integerRange(), boolean (bool in original), function (func in original), regex, stringMatching(), error, null, undefined.

    In the original library, the customProp() validator has to throw an Error object; in this library, it needs to return true or false to indicate the validation result.

    Additionally, the original PropTypes library only logs error strings directly to the console rather than returning an object of information.



    MIT license


    npm i prop-validator

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    • msikma