JavaScript: The Good Parts

A JSON Parser

This is an implementation of a JSON parser in JavaScript:

var json_parse = function () { // This is a function that can parse a JSON text, producing a JavaScript // data structure. It is a simple, recursive descent parser. // We are defining the function inside of another function to avoid creating // global variables. var at, // The index of the current character ch, // The current character escapee = { '"': '"', '\\': '\\', '/': '/', b: 'b', f: '\f', n: '\n', r: '\r', t: '\t' }, text, error = function (m) { // Call error when something is wrong. throw { name: 'SyntaxError', message: m, at: at, text: text }; }, next = function (c) { // If a c parameter is provided, verify that it matches the current character. if (c && c !== ch) { error("Expected '" + c + "' instead of '" + ch + "'"); } // Get the next character. When there are no more characters, // return the empty string. ch = text.charAt(at); at += 1; return ch; }, number = function () { // Parse a number value. var number, string = ''; if (ch === '-') { string = '-'; next('-'); } while (ch >= '0' && ch <= '9') { string += ch; next(); } if (ch === '.') { string += '.'; while (next() && ch >= '0' && ch <= '9') { string += ch; } } if (ch === 'e' || ch === 'E') { string += ch; next(); if (ch === '-' || ch === '+') { string += ch; next(); } while (ch >= '0' && ch <= '9') { string += ch; next(); } } number = +string; if (isNaN(number)) { error("Bad number"); } else { return number; } }, string = function () { // Parse ...