added is.keyValuePair

index.js

@@ -6,6 +6,7 @@ const _is = {
   undefined: require('./src/is-undefined'),
   callable: require('./src/is-callable'),
   emptyString: require('./src/is-empty-string'),
+  keyValuePair: require('./src/is-key-value-pair'),
 
   instance: require('./src/is-instance')
 };
@@ -53,7 +54,7 @@ _is.array = function isArray(val, typeCheck = null) {
 /**
  * Checks if value is of one of valid types specified by `types` array.
  * valid items in `types` are:
- * - `{string}`: type name - one of {'string', 'array', 'numeric', 'object', 'null', 'undefined', 'callable', 'emptyString'}
+ * - `{string}`: type name - one of {'string', 'array', 'numeric', 'object', 'null', 'undefined', 'callable', 'emptyString', 'keyValuePair'}
  * - `{Object}`: instance (eg. Regex) - checks instanceof
  *
  * @param {*} val
@@ -89,6 +90,7 @@ is.null = _is.null;
 is.undefined = _is.undefined;
 is.callable = _is.callable;
 is.emptyString = _is.emptyString;
+is.keyValuePair = _is.keyValuePair;
 
 is.instance = _is.instance;
 

src/is-key-value-pair.js

+const isObject = require('./is-object');
+
+/**
+ * Returns `true` if val is an key-value pair (object with one key and one value); `false` otherwise
+ *
+ * @param {*} val
+ * @returns {Boolean}
+ */
+function isKeyValuePair(val) {
+  return isObject(val) && Object.entries(val).length == 1;
+}
+
+module.exports = isKeyValuePair;

test/test.js

@@ -12,4 +12,7 @@ const { is, force } = require('../index');
 //   is.undefined(undefined)
 // ]);
 
-console.log(is.array(['', '2', ''], 'emptyString'));
+// console.log(is.array(['', '2', ''], 'emptyString'));
+
+console.log(is.keyValuePair({ key: 'value' }));
+console.log(is.keyValuePair({ key: 'value', key2: 'value2' }));