added: [N4S] startsWith rule (#414)

packages/n4s/src/rules/endsWith/spec.js

@@ -24,7 +24,7 @@ describe('Tests isArray rule', () => {
     });
 
     it('Should return false for a suffix longer than the word', () => {
-        expect(endsWith(word, word + 'aaa')).toBe(false);
+        expect(endsWith(word, word.repeat(2))).toBe(false);
     });
 
     it('Should expose negativeForm property', () => {

packages/n4s/src/rules/index.js

@@ -24,6 +24,7 @@ import matches from './matches';
 import numberEquals from './numberEquals';
 import shorterThan from './shorterThan';
 import shorterThanOrEquals from './shorterThanOrEquals';
+import startsWith from './startsWith';
 
 const rules = {
   endsWith,
@@ -50,7 +51,8 @@ const rules = {
   matches,
   numberEquals,
   shorterThan,
-  shorterThanOrEquals
+  shorterThanOrEquals,
+  startsWith
 };
 
 export default extendRules(rules);

packages/n4s/src/rules/spec.js

@@ -27,6 +27,7 @@ const negativeRules = [
   'numberNotEquals',
   'isNotNull',
   'doesNotEndWith',
+  'doesNotStartWith'
 ];
 
 const positiveRules = [
@@ -59,7 +60,8 @@ const positiveRules = [
   'shorterThan',
   'shorterThanOrEquals',
   'isNull',
-  'endsWith'
+  'endsWith',
+  'startsWith'
 ];
 
 const allRules = [...new Set([...positiveRules, ...negativeRules])];

packages/n4s/src/rules/startsWith/index.js

@@ -0,0 +1,7 @@
+function startsWith(value, arg1) {
+    return typeof value === 'string' && typeof arg1 === 'string' && value.startsWith(arg1);
+}
+
+startsWith.negativeForm = 'doesNotStartWith';
+
+export default startsWith;

packages/n4s/src/rules/startsWith/spec.js

@@ -0,0 +1,33 @@
+import startsWith from '.';
+
+describe('Tests isArray rule', () => {
+    const word = 'meow';
+    const totallyDifferentWord = 'lorem';
+    it('Should return true for the same word', () => {
+        expect(startsWith(word, word)).toBe(true);
+    });
+
+    it('Should return true for a prefix', () => {
+        expect(startsWith(word, word.substring(0, word.length / 2))).toBe(true);
+    });
+
+    it('Should return true for empty prefix', () => {
+        expect(startsWith(word, '')).toBe(true);
+    });
+
+    it('Should return false for a wrong prefix', () => {
+        expect(startsWith(word, word.substring(1, word.length - 1))).toBe(false);
+    });
+
+    it('Should return false for a prefix which is a totally different word', () => {
+        expect(startsWith(word, totallyDifferentWord)).toBe(false);
+    });
+
+    it('Should return false for a prefix longer than the word', () => {
+        expect(startsWith(word, word.repeat(2))).toBe(false);
+    });
+
+    it('Should expose negativeForm property', () => {
+        expect(startsWith.negativeForm).toBe('doesNotStartWith');
+    });
+});

packages/vest/docs/enforce.md

@@ -66,6 +66,8 @@ Enforce rules are functions that allow you to test your data against different c
 - [isEven](#iseven)
 - [endsWith](#endswith)
 - [doesNotEndWith](#doesnotendwith)
+- [startsWith](#startsWith)
+- [doesNotStartWith](#doesnotstartwith)
 
 ### equals
 
@@ -1030,6 +1032,39 @@ enforce(true).endsWith(100);
 Determines whether a string does not end with the characters of a specified string.
 Reverse implementation of `endsWith`.
 
+## startsWith
+
+### Description
+
+Determines whether a string starts with the characters of a specified string.
+
+### Usage examples:
+
+```js
+enforce('aba').startsWith('ab');
+enforce('some_string').startsWith('some_');
+enforce('string with spaces').startsWith('string with s');
+enforce('aaaa     ').startsWith('aaaa ');
+// passes
+```
+
+```js
+enforce('for').startsWith('tor');
+enforce('aaaab').startsWith('aab');
+enforce('aa').startsWith('aaa');
+enforce(42).startsWith('b');
+enforce(42).startsWith(50);
+enforce(true).startsWith(100);
+// throws
+```
+
+## doesNotStartWith
+
+### Description
+
+Determines whether a string does not start with the characters of a specified string.
+Reverse implementation of `startsWith`.
+
 # Custom enforce rules
 
 To make it easier to reuse logic across your application, sometimes you would want to encapsulate bits of logic in rules that you can use later on, for example, "what's considered a valid email".

packages/vest/src/typings/vest.d.ts

@@ -136,7 +136,9 @@ export interface IEnforceRules<T = {}> {
   lt: (expected: number | string) => IEnforceRules<T> & EnforceExtendMap<T>;
   lte: (expected: number | string) => IEnforceRules<T> & EnforceExtendMap<T>;
   endsWith: (suffix: string) => IEnforceRules<T> & EnforceExtendMap<T>;
+  startsWith: (prefix: string) => IEnforceRules<T> & EnforceExtendMap<T>;
   doesNotEndWith: (suffix: string) => IEnforceRules<T> & EnforceExtendMap<T>;
+  doesNotStartWith: (prefix: string) => IEnforceRules<T> & EnforceExtendMap<T>;
   numberNotEquals: (
     expected: number | string
   ) => IEnforceRules<T> & EnforceExtendMap<T>;