Added length rule

Author: garrypas

README.md

@@ -36,9 +36,12 @@ Built in rules are:
 - `integer`
 - `decimal`
 - `money`
+- `length`
 
 Decimal can be configured using arguments. e.g `decimal(1,2)` to ensure that (if a decimal point is given) then 1 to 2 digits follow it. `money` allows up to 2 decimal places, any more and it will be invalid.
 
+Length can be configured using arguments. e.g `length(1, 100)` ensures a min length of 1 and max length of 100 characters. You can exclude either parameter to check only the min OR max, for example `length(,100)` ensures a max length of 100 characters.
+
 ## Adding rules
 
 Custom rules can be added

src/index.js

@@ -66,6 +66,14 @@ class Validator {
       integer: (key) => `The ${cleanKey(key)} field must be an integer value.`,
       decimal: (key) => `The ${cleanKey(key)} field must be a decimal value.`,
       money: (key) => `The ${cleanKey(key)} field must be a valid monetary value.`,
+      length: (key, data, args = []) =>
+        `The ${cleanKey(key)} field must be ${
+          args[0] && args[0] !== '0' ? `greater than ${args[0]}` : ''
+        }${
+          args[0] && args[0] !== '0' && args[1] ? ' and ' : ''
+        }${
+          args[1] ? `less than ${args[1]}` : ''
+        } in length.`,
     }
     this.#rules = {
       required: (key, data) => !!data[key].toString() ? undefined : this.#errorMessages.required(key, data),
@@ -77,6 +85,17 @@ class Validator {
       money: (key, data) => data[key] && !createDecimalRegex([1, 2]).test(data[key]) 
         ? this.#errorMessages.money(key, data)
         : undefined,
+      length: (key, data, args = []) => {
+        const minLength = args[0] ? parseInt(args[0]) : 0;
+        const maxLength = args[1] ? parseInt(args[1]) : Number.MAX_SAFE_INTEGER;
+        const value = data[key];
+        if (minLength > maxLength) {
+          throw new Error(`Invalid validation defintion for ${key}; minLength must be smaller than maxLength`)
+        }
+        return value.length < minLength || value.length > maxLength
+          ? this.#errorMessages.length(key, data, args)
+          : undefined;
+      },
     };
   }
 

src/index.test.js

@@ -276,4 +276,26 @@ describe('integration tests', () => {
     expect(result.errors.value).toHaveLength(0);
     expect(result.errorCount).toBe(0);
   });
+
+  [
+    { value: 'abc', minLength: '4', expectedError: 'The value field must be greater than 4 in length.' },
+    { value: 'abcd', minLength: '4', expectedError: undefined },
+    { value: 'abcd', minLength: '0', maxLength: '3', expectedError: 'The value field must be less than 3 in length.' },
+    { value: 'abc', minLength: '0', maxLength: '3', expectedError: undefined },
+    { value: 'abcd', maxLength: '3', expectedError: 'The value field must be less than 3 in length.' },
+    { value: 'abc', maxLength: '3', expectedError: undefined },
+    { value: 'abcd', minLength: '1', maxLength: '3', expectedError: 'The value field must be greater than 1 and less than 3 in length.' },
+  ].forEach(({ value, expectedError, minLength = '', maxLength = '' }) =>
+    test(`should validate "${value}" as ${expectedError ? 'a valid': 'an invalid'} length when size should be in the bounds (${minLength},${maxLength})`, async () => {
+      const result = await validator.validate(
+        { value },
+        { value: `length(${minLength ?? ''},${maxLength ?? ''})`},
+      );
+      if (expectedError) {
+        expect(result.errors.value).toContain(expectedError);
+      }
+      expect(result.errors.value).toHaveLength(expectedError ? 1 : 0);
+      expect(result.errorCount).toBe(expectedError ? 1 : 0);
+    }),
+  );
 })