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devexamples

Validate a Form Against a Schema

Validate a submitted form object against field rules and collect every error at once, so users see all problems instead of one at a time.

JavascriptForm Validation

Code

snippet
export function validateForm(values, rules) {
  const errors = {};
  for (const [field, rule] of Object.entries(rules)) {
    const value = values[field];
    for (const check of rule.checks ?? []) {
      const message = check(value, values);
      if (message) {
        errors[field] = message;
        break;
      }
    }
  }
  return { valid: Object.keys(errors).length === 0, errors };
}

export const required = (label) => (value) =>
  value === undefined || value === null || value === ""
    ? label + " is required"
    : null;

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