initial commit

format.js

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+//
+// format, printf-like string formatting for JavaScript
+// github.com/samsonjs/format
+//
+// Copyright 2010 Sami Samhuri <sami.samhuri@gmail.com>
+// ISC license
+//
+
+var sys = require('sys');
+
+exports.extendNativeStrings = function() {
+    String.prototype.printf = function(/* ... */) {
+        var args = Array.prototype.slice.call(arguments);
+        args.unshift(this);
+        sys.puts(exports.format.apply(this, args));
+    };
+    String.prototype.format = function(/* ... */) {
+        var args = Array.prototype.slice.call(arguments);
+        if (args[0] !== this) args.unshift(this);
+        exports.format.apply(this, args);
+    };
+};
+
+exports.printf = function(/* ... */) {
+    sys.puts(exports.format.apply(this, Array.prototype.slice.call(arguments)));
+};
+
+exports.format = function(format) {
+    var argIndex = 1 // skip initial format argument
+      , args = Array.prototype.slice.call(arguments)
+      , i = 0
+      , n = format.length
+      , result = ''
+      , c
+      , escaped = false
+      , arg
+      , precision
+      , nextArg = function() { return args[argIndex++]; }
+      , slurpNumber = function() {
+              var digits = '';
+              while (format[i].match(/\d/))
+                  digits += format[i++];
+              return digits.length > 0 ? parseInt(digits) : null;
+          }
+      ;
+    for (; i < n; ++i) {
+        c = format[i];
+        if (escaped) {
+            escaped = false;
+            precision = slurpNumber();
+            switch (c) {
+            case 'b': // number in binary
+                result += parseInt(nextArg(), 10).toString(2);
+                break;
+            case 'c': // character
+                arg = nextArg();
+                if (typeof arg === 'string' || arg instanceof String)
+                    result += arg;
+                else
+                    result += String.fromCharCode(parseInt(arg, 10));
+                break;
+            case 'd': // number in decimal
+                result += parseInt(nextArg(), 10);
+                break;
+            case 'f': // floating point number
+                result += parseFloat(nextArg()).toFixed(precision || 6);
+                break;
+            case 'o': // number in octal
+                result += '0' + parseInt(nextArg(), 10).toString(8);
+                break;
+            case 's': // string
+                result += nextArg();
+                break;
+            case 'x': // lowercase hexadecimal
+                result += '0x' + parseInt(nextArg(), 10).toString(16);
+                break;
+            case 'X': // uppercase hexadecimal
+                result += '0x' + parseInt(nextArg(), 10).toString(16).toUpperCase();
+                break;
+            default:
+                result += c;
+                break;
+            }
+        } else if (c === '%') {
+            escaped = true;
+        } else {
+            result += c;
+        }
+    }
+    return result;
+};

test_format.js

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+var format = require('./format');
+format.extendNativeStrings();
+'hello'.printf();
+'hello %s'.printf('sami');
+'b: %b\nc: %c\nd: %d\nf: %f\no: %o\ns: %s\nx: %x\nX: %X'.printf(42, 65, 42*42, 42*42*42/1000000000, 255, 'sami', 0xfeedface, 0xc0ffee);