Map JavaScript undefined to MySQL DEFAULT

README.md

@@ -66,7 +66,8 @@ Different value types are escaped differently, here is how:
   the object. If the property's value is a function, it is skipped; if the
   property's value is an object, toString() is called on it and the returned
   value is used.
-* `undefined` / `null` are converted to `NULL`
+* JavaScript `null` is converted to MySQL `NULL`
+* JavaScript `undefined` is converted to MySQL `DEFAULT`
 * `NaN` / `Infinity` are left as-is. MySQL does not support these, and trying
   to insert them as values will trigger MySQL errors until they implement
   support.

lib/SqlString.js

@@ -31,10 +31,14 @@ SqlString.escapeId = function escapeId(val, forbidQualified) {
 };
 
 SqlString.escape = function escape(val, stringifyObjects, timeZone) {
-  if (val === undefined || val === null) {
+  if (val === null) {
     return 'NULL';
   }
 
+  if (val === undefined) {
+    return 'DEFAULT';
+  }
+
   switch (typeof val) {
     case 'boolean': return (val) ? 'true' : 'false';
     case 'number': return val+'';

test/unit/test-SqlString.js

@@ -35,8 +35,8 @@ test('SqlString.escapeId', {
 });
 
 test('SqlString.escape', {
-  'undefined -> NULL': function() {
-    assert.equal(SqlString.escape(undefined), 'NULL');
+  'undefined -> DEFAULT': function() {
+    assert.equal(SqlString.escape(undefined), 'DEFAULT');
   },
 
   'null -> NULL': function() {