Add typeOf() function. (#381)

* Add typeOf() function.

* Add documentation.

* Remove .swp file

* Fix spacing.

* Respond to PR comments:
* Rename `typeOf()` to `type()`
* Avoid use of Array.includes()

Author: jhorbulyk

docs/object-functions.md

@@ -53,12 +53,27 @@ __Examples__
       "Postcode: SO21 2JN"
     ]
 
- ## `$error()`
+## `$error()`
 __Signature:__`$error(message)`
 
 Deliberately throws an error with an optional `message`
 
- ## `$assert()`
+## `$assert()`
 __Signature:__`$assert(condition, message)`
 
 If condition is true, the function returns undefined. If the condition is false, an exception is thrown with the message as the message of the exception.
+
+## `$type()`
+__Signature:__`$type(value)`
+
+Evaluates the type of `value` and returns one of the following strings:
+* `"null"`
+* `"number"`
+* `"string"`
+* `"boolean"`
+* `"array"`
+* `"object"`
+* `"function"`
+Returns (non-string) `undefined` when `value` is `undefined`.
+
+

src/functions.js

@@ -1841,6 +1841,43 @@ const functions = (() => {
         return undefined;
     }
 
+    /**
+     *
+     * @param {*} [value] - the input to which the type will be checked
+     * @returns {string} - the type of the input
+     */
+    function type(value) {
+        if (value === undefined) {
+            return undefined;
+        }
+
+        if (value === null) {
+            return 'null';
+        }
+
+        if (isNumeric(value)) {
+            return 'number';
+        }
+
+        if (typeof value === 'string') {
+            return 'string';
+        }
+
+        if (typeof value === 'boolean') {
+            return 'boolean';
+        }
+
+        if(Array.isArray(value)) {
+            return 'array';
+        }
+
+        if(isFunction(value)) {
+            return 'function';
+        }
+
+        return 'object';
+    }
+
     /**
      * Implements the merge sort (stable) with optional comparator function
      *
@@ -2014,7 +2051,7 @@ const functions = (() => {
         formatNumber, formatBase, number, floor, ceil, round, abs, sqrt, power, random,
         boolean, not,
         map, zip, filter, single, foldLeft, sift,
-        keys, lookup, append, exists, spread, merge, reverse, each, error, assert, sort, shuffle, distinct,
+        keys, lookup, append, exists, spread, merge, reverse, each, error, assert, type, sort, shuffle, distinct,
         base64encode, base64decode,  encodeUrlComponent, encodeUrl, decodeUrlComponent, decodeUrl
     };
 })();

src/jsonata.js

@@ -1859,6 +1859,7 @@ var jsonata = (function() {
     staticFrame.bind('each', defineFunction(fn.each, '<o-f:a>'));
     staticFrame.bind('error', defineFunction(fn.error, '<s?:x>'));
     staticFrame.bind('assert', defineFunction(fn.assert, '<bs?:x>'));
+    staticFrame.bind('type', defineFunction(fn.type, '<x:s>'));
     staticFrame.bind('sort', defineFunction(fn.sort, '<af?:a>'));
     staticFrame.bind('shuffle', defineFunction(fn.shuffle, '<a:a>'));
     staticFrame.bind('distinct', defineFunction(fn.distinct, '<x:x>'));

test/test-suite/groups/function-typeOf/case001.json

@@ -0,0 +1,6 @@
+{
+    "expr": "($var:= undefined; $type($var))",
+    "dataset": "dataset5",
+    "bindings": {},
+    "undefinedResult": true
+}

test/test-suite/groups/function-typeOf/case002.json

@@ -0,0 +1,6 @@
+{
+    "expr": "($var:= null; $type($var))",
+    "dataset": "dataset5",
+    "bindings": {},
+    "result": "null" 
+}

test/test-suite/groups/function-typeOf/case003.json

@@ -0,0 +1,6 @@
+{
+    "expr": "($var:= 123; $type($var))",
+    "dataset": "dataset5",
+    "bindings": {},
+    "result": "number" 
+}

test/test-suite/groups/function-typeOf/case004.json

@@ -0,0 +1,6 @@
+{
+    "expr": "($var:= '123'; $type($var))",
+    "dataset": "dataset5",
+    "bindings": {},
+    "result": "string" 
+}

test/test-suite/groups/function-typeOf/case005.json

@@ -0,0 +1,6 @@
+{
+    "expr": "($var:= true; $type($var))",
+    "dataset": "dataset5",
+    "bindings": {},
+    "result": "boolean" 
+}

test/test-suite/groups/function-typeOf/case006.json

@@ -0,0 +1,6 @@
+{
+    "expr": "($var:= 'true'; $type($var))",
+    "dataset": "dataset5",
+    "bindings": {},
+    "result": "string" 
+}

test/test-suite/groups/function-typeOf/case007.json

@@ -0,0 +1,6 @@
+{
+    "expr": "($var:= []; $type($var))",
+    "dataset": "dataset5",
+    "bindings": {},
+    "result": "array" 
+}