Add .appendToArray() sindresorhus#109, sindresorhus/electron-store#52

source/index.ts

@@ -223,6 +223,25 @@ class Conf<T extends Record<string, any> = Record<string, unknown>> implements I
 		this.store = store;
 	}
 
+	/**
+    Append an item or multiple items to an array
+
+	@param {key|object} - You can use [dot-notation](https://github.com/sindresorhus/dot-prop) in a key to access nested properties. Or a hashmap of items to set at once.
+	@param value - Must be JSON serializable. Trying to set the type `undefined`, `function`, or `symbol` will result in a `TypeError`.
+    */
+	appendToArray<Key extends keyof T>(key: Key, value: Required<T>[Key]): void;
+	// This overload is used for dot-notation access.
+	appendToArray<Key extends string>(key: Key, value: Required<T>[Key]): void {
+		const list = this.get(key, [] as T[Key]);
+
+		if (!Array.isArray(list)) {
+			throw new TypeError('Config param already set and is not array');
+		}
+
+		list.push(value);
+		this.set(key, list);
+	}
+
 	/**
 	Check if an item exists.
 

test/index.ts

@@ -99,6 +99,17 @@ test('.set() - invalid key', t => {
 	}, {message: 'Expected `key` to be of type `string` or `object`, got number'});
 });
 
+test('.appendToArray()', t => {
+	t.context.config.set('foo', [fixture]);
+	t.context.config.set('baz.boo', [fixture]);
+	t.context.config.appendToArray('foo', '🐴');
+	t.context.config.appendToArray('baz.boo', '🐴');
+	t.context.config.appendToArray('bar', '🐴'); // Will create new item with array
+	t.deepEqual(t.context.config.get('foo'), [fixture, '🐴']);
+	t.deepEqual(t.context.config.get('baz.boo'), [fixture, '🐴']);
+	t.deepEqual(t.context.config.get('bar'), ['🐴']);
+});
+
 test('.has()', t => {
 	t.context.config.set('foo', fixture);
 	t.context.config.set('baz.boo', fixture);