Merge e422143 into 2615b1b

README.md

@@ -119,6 +119,7 @@ You can find the documentations in the [`docs`](./docs) folder or on [`GitBook`]
 * [`stripTags`](./docs/string.md#striptags)
 * [`latinize`](./docs/string.md#latinize)
 * [`wrap`](./docs/string.md#wrap)
+* [`a-or-an`](./docs/string.md#a-or-an)
 * [`with`](./docs/string.md#with)
 * [`reverseStr`](./docs/string.md#reversestr)
 

docs/string.md

@@ -382,6 +382,25 @@ import { WrapPipe } from 'angular-pipes';
 <p>{{ 'foo' | wrap: '{{': '}}' }}</p> <!--result: {{foo}} -->
 ```
 
+#### a-or-an
+
+a-or-an pipe check if string needs to be prepended with `a` or with `an`
+
+Arguments: \( string \)
+
+##### File
+
+```typescript
+import { AorAnPipe } from 'angular-pipes';
+```
+
+##### Usage
+
+```html
+{{'egg' | a-or-an}} <!-- result: 'an egg' -->
+{{'peanut' | a-or-an}} <!-- result: 'a peanut' -->
+```
+
 #### with
 
 With pipe check string has start and/or ends

src/string/a-or-an.pipe.spec.ts

@@ -0,0 +1,54 @@
+import { AorAnPipe } from "./a-or-an.pipe";
+
+describe("AorAnPipe Tests", () => {
+    let pipe: AorAnPipe;
+    beforeEach(() => {
+        pipe = new AorAnPipe();
+    });
+    describe("Misc. Inputs", () => {
+        it('should return "" if passed null', () => {
+            expect(pipe.transform(null)).toEqual("" as string);
+        });
+        it('should return "" if passed undefined', () => {
+            expect(pipe.transform(undefined)).toEqual("" as string);
+        });
+        it('should return "" if passed ""', () => {
+            expect(pipe.transform("")).toEqual("" as string);
+        });
+    });
+    describe("Words Prefixed With 'A'", () => {
+        it('should return "a cat" when passed "cat"', () => {
+            expect(pipe.transform("cat")).toEqual("a cat" as string);
+        });
+    });
+    describe("Words Prefixed With 'An'", () => {
+        it('should return "an egg" if passed "egg"', () => {
+            expect(pipe.transform("egg")).toEqual("an egg" as string);
+        });
+    });
+    describe("Multiple Words", () => {
+        it('should return "an aubergine from the store" if passed "aubergine from the store"', () => {
+            expect(pipe.transform("aubergine from the store")).toEqual("an aubergine from the store" as string);
+        });
+        it('should return "a cat of many colors" if passed "cat of many colors"', () => {
+            expect(pipe.transform("cat of many colors")).toEqual("a cat of many colors" as string);
+        });
+        it('should return "an M.Sc. from a large public Midwestern university" if passed "M.Sc. from a large public Midwestern university"', () => {
+            expect(pipe.transform("M.Sc. from a large public Midwestern university")).toEqual("an M.Sc. from a large public Midwestern university" as string);
+        });
+    });
+    describe("Words from the Irregular Group", () => {
+        it('should return "an herb" if passed "herb"', () => {
+            expect(pipe.transform("herb")).toEqual("an herb" as string);
+        });
+        it('should return "an honor" if passed "honor"', () => {
+            expect(pipe.transform("honor")).toEqual("an honor" as string);
+        });
+        it('should return "an M.Sc." if passed "M.Sc."', () => {
+            expect(pipe.transform("M.Sc.")).toEqual("an M.Sc." as string);
+        });
+        it('should return "a unicorn" if passed "unicorn"', () => {
+            expect(pipe.transform("unicorn")).toEqual("a unicorn" as string);
+        });
+    });
+});

src/string/a-or-an.pipe.ts

@@ -0,0 +1,40 @@
+import { Pipe, PipeTransform } from "@angular/core";
+import { isVowel } from "../utils/utils";
+@Pipe({
+    name: "a-or-an",
+})
+/**
+ * Takes a string and returns the string prepended by 'a' or 'an'.
+ * Uses both naive and holdout-list approaches.
+ * @constructor
+ * @param {string} stringEntity - Entity to prepend 'a' or 'an' to.
+ */
+export class AorAnPipe implements PipeTransform {
+    private irregularMap: any = {
+        aubergine: 'an',
+        herb: 'an',
+        honor: 'an',
+        honorable: 'an',
+        hour: 'an',
+        mba: 'an',
+        msc: 'an',
+        'm.sc.': 'an',
+        umbrella: 'an',
+        unicorn: 'a',
+    };
+    transform(stringEntity: string): string {
+        if (!stringEntity || stringEntity === "") {
+            return "";
+        }
+        else {
+            const firstWord = stringEntity.trim().split(" ")[0];
+            if (this.irregularMap[firstWord.toLocaleLowerCase()]) {
+                return `${this.irregularMap[firstWord.toLocaleLowerCase()]} ${stringEntity}`;
+            } else {
+                return (isVowel(stringEntity[0]))
+                    ? `an ${stringEntity}`
+                    : `a ${stringEntity}`;
+            }
+        }
+    }
+}

src/string/string.module.ts

@@ -22,6 +22,7 @@ import {SlugifyPipe} from './slugify.pipe';
 import {StripTagsPipe} from "./strip-tags.pipe";
 import {LatinizePipe} from "./latinize.pipe";
 import {WrapPipe} from "./wrap.pipe";
+import {AorAnPipe} from "./a-or-an.pipe";
 import {WithPipe} from "./with.pipe";
 import {ReverseStrPipe} from "./reverse-str.pipe";
 
@@ -50,6 +51,7 @@ import {ReverseStrPipe} from "./reverse-str.pipe";
     StripTagsPipe,
     LatinizePipe,
     WrapPipe,
+    AorAnPipe,
     WithPipe,
     ReverseStrPipe
   ],
@@ -76,6 +78,7 @@ import {ReverseStrPipe} from "./reverse-str.pipe";
     StripTagsPipe,
     LatinizePipe,
     WrapPipe,
+    AorAnPipe,
     WithPipe,
     ReverseStrPipe
   ]

src/utils/utils.ts

@@ -42,6 +42,11 @@ export function isString (value: any): value is string {
   return typeof value === 'string';
 }
 
+export function isVowel(letter: string): boolean {
+    const vowels = ["a", "e", "i", "o", "u"];
+    return vowels.indexOf(letter) !== -1;
+}
+
 export function isObject (value: any): boolean {
 
   return value !== null && typeof value === 'object';