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Function signature

function validate(
  schema: SimpleValidationSchema,
  data: Record<string, any>,
  options: ValidationOptions
): string[]
Validates data according to the specified schema and returns an array of error messages. Returns an empty array if validation succeeds.

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Parameters

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schema
SimpleValidationSchema
required
The validation schema that defines the structure and rules for your data. See SimpleValidationSchema for details.
​
data
Record<string, any>
required
The data object to validate. Each key should correspond to a field defined in the schema.
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options
ValidationOptions
required
Validation options including language and custom error messages. See ValidationOptions for details.

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Returns

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errors
string[]
An array of error messages. Each error is formatted as "FieldName: error message". Returns an empty array if validation succeeds.

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Examples

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Basic validation

import { validate } from 'polyval';

const schema = {
  email: {
    type: 'string',
    required: true,
    email: true
  },
  age: {
    type: 'number',
    required: true,
    min: 18
  }
};

const data = {
  email: '[email protected]',
  age: 25
};

const errors = validate(schema, data, { lang: 'en' });
console.log(errors); // []

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Validation with errors

const data = {
  email: 'invalid-email',
  age: 15
};

const errors = validate(schema, data, { lang: 'en' });
console.log(errors);
// [
//   "Email: Must be a valid email address",
//   "Age: Must be at least 18"
// ]

​
Validation with custom messages

const errors = validate(schema, data, {
  lang: 'en',
  customMessages: {
    required: 'This field is mandatory',
    string: {
      email: 'Please enter a valid email address'
    },
    number: {
      min: (min) => `You must be at least ${min} years old`
    }
  }
});
The validate function automatically formats field names by capitalizing the first letter in error messages.

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Error handling

If an unexpected error occurs during validation, the function returns a single-element array: 
['An unexpected validation error occurred']
The validate function catches all exceptions and returns a generic error message. Check the returned array to determine if validation succeeded (empty array) or failed (non-empty array).

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