debug/debug.js

/**
 * This is the common logic for both the Node.js and web browser
 * implementations of `debug()`.
 *
 * Expose `debug()` as the module.
 */

exports = module.exports = debug;
exports.coerce = coerce;
exports.disable = disable;
exports.enable = enable;
exports.enabled = enabled;
exports.humanize = humanize;

/**
 * The currently active debug mode names, and names to skip.
 */

exports.names = [];
exports.skips = [];

/**
 * Map of special "%n" handling functions, for the debug "format" argument.
 *
 * Valid key names are a single, lowercased letter, i.e. "n".
 */

exports.formatters = {};

/**
 * Create a debugger with the given `namespace`.
 *
 * @param {String} namespace
 * @return {Function}
 * @api public
 */

function debug(namespace) {

  // define the `disabled` version
  function disabled() {
  }
  disabled.enabled = false;

  // define the `enabled` version
  function enabled() {
    var args = Array.prototype.slice.call(arguments);
    if ('string' === typeof args[0]) {
      args[0] = exports.coerce(args[0]);
    } else {
      // anything else let's inspect with %o
      args = ['%o'].concat(args);
    }

    // apply any `formatters` transformations
    var index = 0;
    args[0] = args[0].replace(/%([a-z%])/g, function(match, format) {
      // if we encounter an escaped % then don't increase the array index
      if (match === '%%') return match;
      index++;
      var formatter = exports.formatters[format];
      if ('function' === typeof formatter) {
        var val = args[index];
        match = formatter.call(enabled, val);

        // now we need to remove `args[index]` since it's inlined in the `format`
        args.splice(index, 1);
        index--;
      }
      return match;
    });

    exports.log.apply(enabled, args);
  }
  enabled.enabled = true;

  var fn = exports.enabled(namespace) ? enabled : disabled;

  fn.namespace = namespace;

  return fn;
}

/**
 * Enables a debug mode by namespaces. This can include modes
 * separated by a colon and wildcards.
 *
 * @param {String} namespaces
 * @api public
 */

function enable(namespaces) {
  exports.save(namespaces);

  var split = (namespaces || '').split(/[\s,]+/);
  var len = split.length;

  for (var i = 0; i < len; i++) {
    namespaces = split[i].replace('*', '.*?');
    if (namespaces[0] === '-') {
      exports.skips.push(new RegExp('^' + namespaces.substr(1) + '$'));
    } else {
      exports.names.push(new RegExp('^' + namespaces + '$'));
    }
  }
}

/**
 * Disable debug output.
 *
 * @api public
 */

function disable() {
  exports.enable('');
}

/**
 * Humanize the given `ms`.
 *
 * @param {Number} m
 * @return {String}
 * @api private
 */

function humanize(ms) {
  var sec = 1000;
  var min = 60 * 1000;
  var hour = 60 * min;

  if (ms >= hour) return (ms / hour).toFixed(1) + 'h';
  if (ms >= min) return (ms / min).toFixed(1) + 'm';
  if (ms >= sec) return (ms / sec | 0) + 's';
  return ms + 'ms';
}

/**
 * Returns true if the given mode name is enabled, false otherwise.
 *
 * @param {String} name
 * @return {Boolean}
 * @api public
 */

function enabled(name) {
  var i, len;
  for (i = 0, len = exports.skips.length; i < len; i++) {
    if (exports.skips[i].test(name)) {
      return false;
    }
  }
  for (i = 0, len = exports.names.length; i < len; i++) {
    if (exports.names[i].test(name)) {
      return true;
    }
  }
  return false;
}

/**
 * Coerce `val`.
 *
 * @param {Mixed} val
 * @return {Mixed}
 * @api private
 */

function coerce(val) {
  if (val instanceof Error) return val.stack || val.message;
  return val;
}