Adds type option

README.md

@@ -25,10 +25,13 @@ The placeholders in the format string are marked by `%` and are followed by one
     * `o` — yields an integer as an octal number
     * `s` — yields a string as is
     * `t` — yields `true` or `false`
+    * `T` — yields the type of the argument<sup>[1](#fn1)</sup>
     * `x` — yields an integer as a hexadecimal number (lower-case)
     * `X` — yields an integer as a hexadecimal number (upper-case)
     * `j` — yields a JavaScript object or array as a JSON encoded string
 
+<a name="fn1">1</a> `sprintf` doesn't use the `typeof` operator. As such, the value `null` is a `null`, an array is an `array` (not an `object`), a date value is a `date` etc.
+
 ## JavaScript `vsprintf`
 `vsprintf` is the same as `sprintf` except that it accepts an array of arguments, rather than a variable number of arguments:
 

src/sprintf.js

@@ -2,12 +2,14 @@
     var re = {
         not_string: /[^s]/,
         not_bool: /[^t]/,
+        not_type: /[^T]/,
         number: /[diefg]/,
+        numeric_arg: /bcdiefguxX/,
         json: /[j]/,
         not_json: /[^j]/,
         text: /^[^\x25]+/,
         modulo: /^\x25{2}/,
-        placeholder: /^\x25(?:([1-9]\d*)\$|\(([^\)]+)\))?(\+)?(0|'[^$])?(-)?(\d+)?(?:\.(\d+))?([b-gijostuxX])/,
+        placeholder: /^\x25(?:([1-9]\d*)\$|\(([^\)]+)\))?(\+)?(0|'[^$])?(-)?(\d+)?(?:\.(\d+))?([b-gijostTuxX])/,
         key: /^([a-z_][a-z_\d]*)/i,
         key_access: /^\.([a-z_][a-z_\d]*)/i,
         index_access: /^\[(\d+)\]/,
@@ -47,11 +49,11 @@
                     arg = argv[cursor++]
                 }
 
-                if (get_type(arg) == 'function') {
+                if (re.not_type.test(match[8]) && get_type(arg) == 'function') {
                     arg = arg()
                 }
 
-                if (re.not_string.test(match[8]) && re.not_bool.test(match[8]) && re.not_json.test(match[8]) && (get_type(arg) != 'number' && isNaN(arg))) {
+                if (re.numeric_arg.test(match[8]) && (get_type(arg) != 'number' && isNaN(arg))) {
                     throw new TypeError(sprintf("[sprintf] expecting number but found %s", get_type(arg)))
                 }
 
@@ -92,6 +94,10 @@
                         arg = String(!!arg)
                         arg = (match[6] ? arg.substring(0, match[6]) : arg)
                     break
+                    case 'T':
+                        arg = get_type(arg)
+                        arg = (match[6] ? arg.substring(0, match[6]) : arg)
+                    break
                     case 'u':
                         arg = parseInt(arg, 10) >>> 0
                     break