type coercion...

Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>

js-types-n-oop.js

@@ -149,7 +149,32 @@
 
 // Automatic type coercion
 //
-// XXX
+// In JavaScript most operations are defined on operands of the same 
+// type. If the types are different JavaScript will try and convert 
+// one of the values to make the types match.
+//
+// In most cases this is fully transparent, for example:
+	'42' == 42 // -> true
+	2 * '21' // -> 42
+	undefined == null // -> true
+
+// But in cases where the same operation is defined for both types
+// the result may seem less predictable, for example `+` defines both
+// number addition and string concatination:
+	1 + 2 // -> 3
+	'a' + 'b' // -> 'ab'
+
+// But when mixed it reverts to constructor:
+	1 + '2' // -> '12'
+
+// This feature can both help make the code simpler and more generic if
+// used conciously and at the same time can prove quite frustrating if
+// neglected.
+//
+// This neglect and carelessness is the main reason it is quite popular
+// to avoid type coercion and instead overuse strict comparisons and 
+// deffensively over-check everything, at times raised to such levels as
+// to define whole languages (like TypeScript) around this.
 
 
 // Type checking