Merge pull request #2 from MikeIbberson/feat/negatives

Negative comparisons

README.md

@@ -6,20 +6,25 @@
 <img src='https://bettercodehub.com/edge/badge/MikeIbberson/comparisons?branch=master'>
 </p> 
 
-<p>Currently, expressions support <code>=</code>, <code>>=</code>, <code><=</code>, <code>></code> and <code><</code> operators. Optionally, you can include a second constructor argument for changing the locale (the default is "en"). Any expressions that do not match a recognized operation get stripped out and are assumed to pass. For simply matching if a property exists, use the <code>=*</code> expression.</p>
+<p>Currently, expressions support <code>=</code>, <code>>=</code>, <code><=</code>, <code>></code>, <code><</code> and <code>!=</code> operators. Optionally, you can include a second constructor argument for changing the locale (the default is "en"). Any expressions that do not match a recognized operation get stripped out and are assumed to pass.</p>
+
+<p>For simply matching if a property exists, use the <code>=*</code> expression. Likewise, use the <code>!</code> flag on the key name to check for missing/empty values.</p>
 
 <p>Don't worry about type casting&mdash;we'll handle that for you.</p>
 
+<h2>Example usage</h2>
+
+```Bash
+  # Or use npm install
+  yarn add comparisons
+```
+
 ```Javascript
-// @TODO yarn add comparisons
 const Comparison = require('comparisons');
 
-const tests = ['foo=bar', 'num>=2'];
+const tests = ['foo=bar', 'num>=2', '!quuz'];
 const stub = { foo: 'bar', num: 3 };
 const runner =  new  Comparison(tests);
 runner.eval(stub); // returns true or false
 runner.query(); // returns a Mongo friendly query
 ```
-
-<h2>Coming Soon</h2>
-I'd like to implement non-matching operators into this as well so we can compare against differences.

lib/__tests__/comparison.test.js

@@ -8,9 +8,11 @@ const exp = [
   'language=EN',
   'bestFriend.name=jon',
   'colleague.age=*',
+  '!colour',
 ];
 
 const stub = {
+  colour: null,
   foo: 'bar',
   age: 21,
   language: 'en',
@@ -29,6 +31,7 @@ describe('Comparison', () => {
       expect(Comparison.isValid('<')).toBeTruthy();
       expect(Comparison.isValid('>=')).toBeTruthy();
       expect(Comparison.isValid('<=')).toBeTruthy();
+      expect(Comparison.isValid('!foo')).toBeTruthy();
     });
   });
 
@@ -38,7 +41,9 @@ describe('Comparison', () => {
 
     it('should return falsy', () =>
       expect(
-        new Comparison(['age>22', 'language=FR']).eval(stub),
+        new Comparison(['age>22', 'language=FR', 'color=red']).eval(
+          stub,
+        ),
       ).toBeFalsy());
   });
 
@@ -52,6 +57,7 @@ describe('Comparison', () => {
           { language: /EN/gi },
           { 'bestFriend.name': /jon/gi },
           { 'colleague.age': { $exists: true } },
+          { 'colour': { $or: [{ $exists: false }, { $eq: null }] } },
         ],
       }));
 

lib/__tests__/utils.test.js

@@ -38,6 +38,17 @@ describe('Utils', () => {
       expect(Utils.equals('a', '*')).toBeTruthy());
   });
 
+  describe('"doesNotEqual"', () => {
+    it('should return truthy', () =>
+      expect(Utils.doesNotEqual('foo', 'bar')).toBeTruthy());
+
+    it('should return falsy', () =>
+      expect(Utils.doesNotEqual('foo', 'foo')).toBeFalsy());
+
+    it('should return falsy', () =>
+      expect(Utils.doesNotEqual(2, 2)).toBeFalsy());
+  });
+
   describe('isGreaterThan', () => {
     it('should return truthy on numerics', () =>
       expect(Utils.isGreaterThan(123, 12)).toBeTruthy());
@@ -97,4 +108,15 @@ describe('Utils', () => {
     it('should return truthy on equal value', () =>
       expect(Utils.isGreaterThanOrEqualTo(1, 2)).toBeFalsy());
   });
+
+  describe('isEmpty', () => {
+    it('should return truthy on null', () =>
+      expect(Utils.isEmpty(null)).toBeTruthy());
+
+    it('should return truthy on undefined', () =>
+      expect(Utils.isEmpty(undefined)).toBeTruthy());
+
+    it('should return falsy on false', () =>
+      expect(Utils.isEmpty(false)).toBeFalsy());
+  });
 });

lib/index.js

@@ -2,10 +2,12 @@ const flat = require('flat');
 
 const {
   equals,
+  doesNotEqual,
   isGreaterThan,
   isLessThan,
   isGreaterThanOrEqualTo,
   isLessThanOrEqualTo,
+  isEmpty,
   cast,
 } = require('./utils');
 
@@ -15,10 +17,12 @@ const ops = {
   '>': isGreaterThan,
   '<': isLessThan,
   '=': equals,
+  '!=': doesNotEqual,
 };
 
 const getAssignment = {
   'equals': cast,
+  'isEmpty': cast,
   'isLessThan': (v) => ({
     $lt: cast(v),
   }),
@@ -37,18 +41,23 @@ const keys = Object.keys(ops);
 const re = new RegExp(`[${keys.map((v) => `(${v})`).join('')}]`, 'i');
 
 const hasLength = (v) => Array.isArray(v) && v.length;
+const hasNegation = (v) => typeof v === 'string' && v.startsWith('!');
 
 const getOp = (v) =>
-  keys.reduce(
-    (a, c) =>
-      v.includes(c) && !hasLength(a)
-        ? v
-            .split(re)
-            .filter(Boolean)
-            .concat(ops[c])
-        : a,
-    [],
-  );
+  hasNegation(v)
+    ? // reference the cast function conditionals
+      // this leverages how wildcards work, just the inverse
+      [v.replace('!', ''), '!', isEmpty]
+    : keys.reduce(
+        (a, c) =>
+          v.includes(c) && !hasLength(a)
+            ? v
+                .split(re)
+                .filter(Boolean)
+                .concat(ops[c])
+            : a,
+        [],
+      );
 
 class Comparison {
   constructor(exp, locale = 'en') {
@@ -57,7 +66,7 @@ class Comparison {
   }
 
   static isValid(v) {
-    return re.test(v);
+    return hasNegation(v) || re.test(v);
   }
 
   get eligible() {

lib/utils.js

@@ -58,16 +58,19 @@ class ValidatorRunner {
   }
 }
 
+const runCompare = (a, b, locale) =>
+  String(a).localeCompare(String(b), locale, {
+    sensitivity: 'base',
+  });
+
 const equals = (a, b, locale) => {
   if (b === '*') return a !== '' && a !== undefined && a !== null;
 
-  return (
-    String(a).localeCompare(String(b), locale, {
-      sensitivity: 'base',
-    }) === 0
-  );
+  return runCompare(a, b, locale) === 0;
 };
 
+const doesNotEqual = (a, b, locale) => runCompare(a, b, locale) !== 0;
+
 const isGreaterThan = (a, b) =>
   new ValidatorRunner([a, b]).sequence([
     'isGreaterThanNumeric',
@@ -90,19 +93,25 @@ const isLessThanOrEqualTo = (a, b, locale) =>
 
 const cast = (v) => {
   if (v === '*') return { $exists: true };
+  if (v === '!') return { $or: [{ $exists: false }, { $eq: null }] };
 
   const test = validate(v);
   if (test.date()) return v;
   if (test.numeric()) return parseFloat(v);
   return new RegExp(v, 'i');
 };
 
+const isEmpty = (v) =>
+  v === undefined || v === null || v === 'undefined' || v === 'null';
+
 module.exports = {
   equals,
+  doesNotEqual,
   isGreaterThan,
   isLessThan,
   isGreaterThanOrEqualTo,
   isLessThanOrEqualTo,
+  isEmpty,
   validate,
   cast,
 };

package.json

@@ -1,6 +1,6 @@
 {
   "name": "comparisons",
-  "version": "2.0.3",
+  "version": "2.1.1",
   "main": "lib/index.js",
   "license": "MIT",
   "jest": {