Add is.empty() (#16)

index.js

@@ -163,4 +163,10 @@ is.inRange = (x, range) => {
 
 is.infinite = x => x === Infinity || x === -Infinity;
 
+const isEmptyStringOrArray = x => (is.string(x) || is.array(x)) && x.length === 0;
+const isEmptyObject = x => !is.map(x) && !is.set(x) && is.object(x) && Object.keys(x).length === 0;
+const isEmptyMapOrSet = x => (is.map(x) || is.set(x)) && x.size === 0;
+
+is.empty = x => !x || isEmptyStringOrArray(x) || isEmptyObject(x) || isEmptyMapOrSet(x);
+
 module.exports = is;

readme.md

@@ -150,6 +150,11 @@ is.inRange(3, 10);
 Check if `value` is `Infinity` or `-Infinity`.
 
 
+##### .empty(value)
+
+Returns `true` if `value` is falsy or an empty string, array, object, map, or set.
+
+
 ## FAQ
 
 ### Why yet another type checking module?

test.js

@@ -373,3 +373,32 @@ test('is.inRange', t => {
 test('is.infinite', t => {
 	testType(t, 'infinite', ['number']);
 });
+
+test('is.empty', t => {
+	t.true(m.empty(null));
+	t.true(m.empty(undefined));
+
+	t.true(m.empty(false));
+	t.false(m.empty(true));
+
+	t.true(m.empty(''));
+	t.false(m.empty('🦄'));
+
+	t.true(m.empty([]));
+	t.false(m.empty(['🦄']));
+
+	t.true(m.empty({}));
+	t.false(m.empty({unicorn: '🦄'}));
+
+	const tempMap = new Map();
+	t.true(m.empty(tempMap));
+
+	tempMap.set('unicorn', '🦄');
+	t.false(m.empty(tempMap));
+
+	const tempSet = new Set();
+	t.true(m.empty(tempSet));
+
+	tempSet.add(1);
+	t.false(m.empty(tempSet));
+});