JavaScript sprintf

JavaScript sprintf 

string sprintf(string format , [mixed arg1 [, mixed arg2 [ ,...]]]);

A type specifier that can be any of:

  • % — print a literal “%” character
  • b — print an integer as a binary number
  • c — print an integer as the character with that ASCII value
  • d — print an integer as a signed decimal number
  • e — print a float as scientific notation
  • u — print an integer as an unsigned decimal number
  • f — print a float as is
  • o — print an integer as an octal number
  • s — print a string as is
  • x — print an integer as a hexadecimal number (lower-case)
  • X — print an integer as a hexadecimal number (upper-case)
var sprintf = (function() {
	function get_type(variable) {
		return Object.prototype.toString.call(variable).slice(8, -1).toLowerCase();
	}
	function str_repeat(input, multiplier) {
		for (var output = []; multiplier > 0; output[--multiplier] = input) {/* do nothing */}
		return output.join('');
	}

	var str_format = function() {
		if (!str_format.cache.hasOwnProperty(arguments[0])) {
			str_format.cache[arguments[0]] = str_format.parse(arguments[0]);
		}
		return str_format.format.call(null, str_format.cache[arguments[0]], arguments);
	};

	str_format.format = function(parse_tree, argv) {
		var cursor = 1, tree_length = parse_tree.length, node_type = '', arg, output = [], i, k, match, pad, pad_character, pad_length;
		for (i = 0; i < tree_length; i++) {
			node_type = get_type(parse_tree[i]);
			if (node_type === 'string') {
				output.push(parse_tree[i]);
			}
			else if (node_type === 'array') {
				match = parse_tree[i]; // convenience purposes only
				if (match[2]) { // keyword argument
					arg = argv[cursor];
					for (k = 0; k < match[2].length; k++) { 						if (!arg.hasOwnProperty(match[2][k])) { 							throw(sprintf('[sprintf] property "%s" does not exist', match[2][k])); 						} 						arg = arg[match[2][k]]; 					} 				} 				else if (match[1]) { // positional argument (explicit) 					arg = argv[match[1]]; 				} 				else { // positional argument (implicit) 					arg = argv[cursor++]; 				} 				if (/[^s]/.test(match[8]) && (get_type(arg) != 'number')) { 					throw(sprintf('[sprintf] expecting number but found %s', get_type(arg))); 				} 				switch (match[8]) { 					case 'b': arg = arg.toString(2); break; 					case 'c': arg = String.fromCharCode(arg); break; 					case 'd': arg = parseInt(arg, 10); break; 					case 'e': arg = match[7] ? arg.toExponential(match[7]) : arg.toExponential(); break; 					case 'f': arg = match[7] ? parseFloat(arg).toFixed(match[7]) : parseFloat(arg); break; 					case 'o': arg = arg.toString(8); break; 					case 's': arg = ((arg = String(arg)) && match[7] ? arg.substring(0, match[7]) : arg); break; 					case 'u': arg = Math.abs(arg); break; 					case 'x': arg = arg.toString(16); break; 					case 'X': arg = arg.toString(16).toUpperCase(); break; 				} 				arg = (/[def]/.test(match[8]) && match[3] && arg >= 0 ? '+'+ arg : arg);
				pad_character = match[4] ? match[4] == '0' ? '0' : match[4].charAt(1) : ' ';
				pad_length = match[6] - String(arg).length;
				pad = match[6] ? str_repeat(pad_character, pad_length) : '';
				output.push(match[5] ? arg + pad : pad + arg);
			}
		}
		return output.join('');
	};

	str_format.cache = {};

	str_format.parse = function(fmt) {
		var _fmt = fmt, match = [], parse_tree = [], arg_names = 0;
		while (_fmt) {
			if ((match = /^[^\x25]+/.exec(_fmt)) !== null) {
				parse_tree.push(match[0]);
			}
			else if ((match = /^\x25{2}/.exec(_fmt)) !== null) {
				parse_tree.push('%');
			}
			else if ((match = /^\x25(?:([1-9]\d*)\$|\(([^\)]+)\))?(\+)?(0|'[^$])?(-)?(\d+)?(?:\.(\d+))?([b-fosuxX])/.exec(_fmt)) !== null) {
				if (match[2]) {
					arg_names |= 1;
					var field_list = [], replacement_field = match[2], field_match = [];
					if ((field_match = /^([a-z_][a-z_\d]*)/i.exec(replacement_field)) !== null) {
						field_list.push(field_match[1]);
						while ((replacement_field = replacement_field.substring(field_match[0].length)) !== '') {
							if ((field_match = /^\.([a-z_][a-z_\d]*)/i.exec(replacement_field)) !== null) {
								field_list.push(field_match[1]);
							}
							else if ((field_match = /^\[(\d+)\]/.exec(replacement_field)) !== null) {
								field_list.push(field_match[1]);
							}
							else {
								throw('[sprintf] huh?');
							}
						}
					}
					else {
						throw('[sprintf] huh?');
					}
					match[2] = field_list;
				}
				else {
					arg_names |= 2;
				}
				if (arg_names === 3) {
					throw('[sprintf] mixing positional and named placeholders is not (yet) supported');
				}
				parse_tree.push(match);
			}
			else {
				throw('[sprintf] huh?');
			}
			_fmt = _fmt.substring(match[0].length);
		}
		return parse_tree;
	};

	return str_format;
})();

var vsprintf = function(fmt, argv) {
	argv.unshift(fmt);
	return sprintf.apply(null, argv);
};

 

 

 

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