Add option to merge extracted strings with existing translations (Thanks to @ocombe)

src/utils/translation.collection.ts

@@ -0,0 +1,69 @@
+export interface TranslationType {
+	[key: string]: string
+};
+
+export class TranslationCollection {
+
+	public values: TranslationType = {};
+
+	public constructor(values: TranslationType = {}) {
+		this.values = values;
+	}
+
+	public add(key: string, val: string = ''): TranslationCollection {
+		return new TranslationCollection(Object.assign({}, this.values, { [key]: val }));
+	}
+
+	public addKeys(keys: string[]): TranslationCollection {
+		const values = keys.reduce((results, key) => {
+			results[key] = '';
+			return results;
+		}, {});
+		return new TranslationCollection(Object.assign({}, this.values, values));
+	}
+
+	public remove(key: string): TranslationCollection {
+		let newCollection = new TranslationCollection();
+		Object.keys(this.values).forEach(collectionKey => {
+			if (key !== collectionKey) {
+				newCollection = newCollection.add(key, this.values[key]);
+			}
+		});
+		return newCollection;
+	}
+
+	public union(collection: TranslationCollection): TranslationCollection {
+		return new TranslationCollection(Object.assign({}, this.values, collection.values));
+	}
+
+	public intersect(collection: TranslationCollection): TranslationCollection {
+		let newCollection = new TranslationCollection();
+		Object.keys(this.values).forEach(key => {
+			if (collection.has(key)) {
+				newCollection = newCollection.add(key, this.values[key]);
+			}
+		});
+		return newCollection;
+	}
+
+	public has(key: string): boolean {
+		return this.values.hasOwnProperty(key);
+	}
+
+	public get(key: string): string {
+		return this.values[key];
+	}
+
+	public keys(): string[] {
+		return Object.keys(this.values);
+	}
+
+	public count(): number {
+		return Object.keys(this.values).length;
+	}
+
+	public isEmpty(): boolean {
+		return Object.keys(this.values).length === 0;
+	}
+
+}