util: remove duplicate code in format

util.format contains an idential if statement within each branch
of switch. Move it before the switch statement for cleaner code
and better performance.

PR-URL: https://github.com/nodejs/node/pull/15098
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/util.js

@@ -111,51 +111,35 @@ function format(f) {
         ++i;
         continue;
       }
-      switch (f.charCodeAt(i + 1)) {
-        case 100: // 'd'
       if (lastPos < i)
         str += f.slice(lastPos, i);
+      switch (f.charCodeAt(i + 1)) {
+        case 100: // 'd'
           str += Number(arguments[a++]);
           break;
         case 105: // 'i'
-          if (lastPos < i)
-            str += f.slice(lastPos, i);
           str += parseInt(arguments[a++]);
           break;
         case 102: // 'f'
-          if (lastPos < i)
-            str += f.slice(lastPos, i);
           str += parseFloat(arguments[a++]);
           break;
         case 106: // 'j'
-          if (lastPos < i)
-            str += f.slice(lastPos, i);
           str += tryStringify(arguments[a++]);
           break;
         case 115: // 's'
-          if (lastPos < i)
-            str += f.slice(lastPos, i);
           str += String(arguments[a++]);
           break;
         case 79: // 'O'
-          if (lastPos < i)
-            str += f.slice(lastPos, i);
           str += inspect(arguments[a++]);
           break;
         case 111: // 'o'
-          if (lastPos < i)
-            str += f.slice(lastPos, i);
           str += inspect(arguments[a++],
                          { showHidden: true, depth: 4, showProxy: true });
           break;
         case 37: // '%'
-          if (lastPos < i)
-            str += f.slice(lastPos, i);
           str += '%';
           break;
         default: // any other character is not a correct placeholder
-          if (lastPos < i)
-            str += f.slice(lastPos, i);
           str += '%';
           lastPos = i = i + 1;
           continue;