inspect.js

// This is (almost) directly from Node.js utils
// https://github.com/joyent/node/blob/f8c335d0caf47f16d31413f89aa28eda3878e3aa/lib/util.js

var getName = require('get-func-name');
var getProperties = require('./getProperties');
var getEnumerableProperties = require('./getEnumerableProperties');
var config = require('../config');

module.exports = inspect;

/**
 * ### .inspect(obj, [showHidden], [depth], [colors])
 *
 * Echoes the value of a value. Tries to print the value out
 * in the best way possible given the different types.
 *
 * @param {Object} obj The object to print out.
 * @param {Boolean} showHidden Flag that shows hidden (not enumerable)
 *    properties of objects. Default is false.
 * @param {Number} depth Depth in which to descend in object. Default is 2.
 * @param {Boolean} colors Flag to turn on ANSI escape codes to color the
 *    output. Default is false (no coloring).
 * @namespace Utils
 * @name inspect
 */
function inspect(obj, showHidden, depth, colors) {
  var ctx = {
    showHidden: showHidden,
    seen: [],
    stylize: function (str) { return str; }
  };
  return formatValue(ctx, obj, (typeof depth === 'undefined' ? 2 : depth));
}

// Returns true if object is a DOM element.
var isDOMElement = function (object) {
  if (typeof HTMLElement === 'object') {
    return object instanceof HTMLElement;
  } else {
    return object &&
      typeof object === 'object' &&
      'nodeType' in object &&
      object.nodeType === 1 &&
      typeof object.nodeName === 'string';
  }
};

function formatValue(ctx, value, recurseTimes) {
  // Provide a hook for user-specified inspect functions.
  // Check that value is an object with an inspect function on it
  if (value && typeof value.inspect === 'function' &&
      // Filter out the util module, it's inspect function is special
      value.inspect !== exports.inspect &&
      // Also filter out any prototype objects using the circular check.
      !(value.constructor && value.constructor.prototype === value)) {
    var ret = value.inspect(recurseTimes, ctx);
    if (typeof ret !== 'string') {
      ret = formatValue(ctx, ret, recurseTimes);
    }
    return ret;
  }

  // Primitive types cannot have properties
  var primitive = formatPrimitive(ctx, value);
  if (primitive) {
    return primitive;
  }

  // If this is a DOM element, try to get the outer HTML.
  if (isDOMElement(value)) {
    if ('outerHTML' in value) {
      return value.outerHTML;
      // This value does not have an outerHTML attribute,
      //   it could still be an XML element
    } else {
      // Attempt to serialize it
      try {
        if (document.xmlVersion) {
          var xmlSerializer = new XMLSerializer();
          return xmlSerializer.serializeToString(value);
        } else {
          // Firefox 11- do not support outerHTML
          //   It does, however, support innerHTML
          //   Use the following to render the element
          var ns = "http://www.w3.org/1999/xhtml";
          var container = document.createElementNS(ns, '_');

          container.appendChild(value.cloneNode(false));
          var html = container.innerHTML
            .replace('><', '>' + value.innerHTML + '<');
          container.innerHTML = '';
          return html;
        }
      } catch (err) {
        // This could be a non-native DOM implementation,
        //   continue with the normal flow:
        //   printing the element as if it is an object.
      }
    }
  }

  // Look up the keys of the object.
  var visibleKeys = getEnumerableProperties(value);
  var keys = ctx.showHidden ? getProperties(value) : visibleKeys;

  var name, nameSuffix;

  // Some type of object without properties can be shortcut.
  // In IE, errors have a single `stack` property, or if they are vanilla `Error`,
  // a `stack` plus `description` property; ignore those for consistency.
  if (keys.length === 0 || (isError(value) && (
      (keys.length === 1 && keys[0] === 'stack') ||
      (keys.length === 2 && keys[0] === 'description' && keys[1] === 'stack')
     ))) {
    if (typeof value === 'function') {
      name = getName(value);
      nameSuffix = name ? ': ' + name : '';
      return ctx.stylize('[Function' + nameSuffix + ']', 'special');
    }
    if (isRegExp(value)) {
      return ctx.stylize(RegExp.prototype.toString.call(value), 'regexp');
    }
    if (isDate(value)) {
      return ctx.stylize(Date.prototype.toUTCString.call(value), 'date');
    }
    if (isError(value)) {
      return formatError(value);
    }
  }

  var base = ''
    , array = false
    , typedArray = false
    , braces = ['{', '}'];

  if (isTypedArray(value)) {
    typedArray = true;
    braces = ['[', ']'];
  }

  // Make Array say that they are Array
  if (isArray(value)) {
    array = true;
    braces = ['[', ']'];
  }

  // Make functions say that they are functions
  if (typeof value === 'function') {
    name = getName(value);
    nameSuffix = name ? ': ' + name : '';
    base = ' [Function' + nameSuffix + ']';
  }

  // Make RegExps say that they are RegExps
  if (isRegExp(value)) {
    base = ' ' + RegExp.prototype.toString.call(value);
  }

  // Make dates with properties first say the date
  if (isDate(value)) {
    base = ' ' + Date.prototype.toUTCString.call(value);
  }

  // Make error with message first say the error
  if (isError(value)) {
    return formatError(value);
  }

  if (keys.length === 0 && (!array || value.length == 0)) {
    return braces[0] + base + braces[1];
  }

  if (recurseTimes < 0) {
    if (isRegExp(value)) {
      return ctx.stylize(RegExp.prototype.toString.call(value), 'regexp');
    } else {
      return ctx.stylize('[Object]', 'special');
    }
  }

  ctx.seen.push(value);

  var output;
  if (array) {
    output = formatArray(ctx, value, recurseTimes, visibleKeys, keys);
  } else if (typedArray) {
    return formatTypedArray(value);
  } else {
    output = keys.map(function(key) {
      return formatProperty(ctx, value, recurseTimes, visibleKeys, key, array);
    });
  }

  ctx.seen.pop();

  return reduceToSingleString(output, base, braces);
}

function formatPrimitive(ctx, value) {
  switch (typeof value) {
    case 'undefined':
      return ctx.stylize('undefined', 'undefined');

    case 'string':
      var simple = '\'' + JSON.stringify(value).replace(/^"|"$/g, '')
                                               .replace(/'/g, "\\'")
                                               .replace(/\\"/g, '"') + '\'';
      return ctx.stylize(simple, 'string');

    case 'number':
      if (value === 0 && (1/value) === -Infinity) {
        return ctx.stylize('-0', 'number');
      }
      return ctx.stylize('' + value, 'number');

    case 'boolean':
      return ctx.stylize('' + value, 'boolean');

    case 'symbol':
      return ctx.stylize(value.toString(), 'symbol');

    case 'bigint':
      return ctx.stylize(value.toString() + 'n', 'bigint');
  }
  // For some reason typeof null is "object", so special case here.
  if (value === null) {
    return ctx.stylize('null', 'null');
  }
}

function formatError(value) {
  return '[' + Error.prototype.toString.call(value) + ']';
}

function formatArray(ctx, value, recurseTimes, visibleKeys, keys) {
  var output = [];
  for (var i = 0, l = value.length; i < l; ++i) {
    if (Object.prototype.hasOwnProperty.call(value, String(i))) {
      output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
          String(i), true));
    } else {
      output.push('');
    }
  }

  keys.forEach(function(key) {
    if (!key.match(/^\d+$/)) {
      output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
          key, true));
    }
  });
  return output;
}

function formatTypedArray(value) {
  var str = '[ ';

  for (var i = 0; i < value.length; ++i) {
    if (str.length >= config.truncateThreshold - 7) {
      str += '...';
      break;
    }
    str += value[i] + ', ';
  }
  str += ' ]';

  // Removing trailing `, ` if the array was not truncated
  if (str.indexOf(',  ]') !== -1) {
    str = str.replace(',  ]', ' ]');
  }

  return str;
}

function formatProperty(ctx, value, recurseTimes, visibleKeys, key, array) {
  var name;
  var propDescriptor = Object.getOwnPropertyDescriptor(value, key);
  var str;

  if (propDescriptor) {
    if (propDescriptor.get) {
      if (propDescriptor.set) {
        str = ctx.stylize('[Getter/Setter]', 'special');
      } else {
        str = ctx.stylize('[Getter]', 'special');
      }
    } else {
      if (propDescriptor.set) {
        str = ctx.stylize('[Setter]', 'special');
      }
    }
  }
  if (visibleKeys.indexOf(key) < 0) {
    name = '[' + key + ']';
  }
  if (!str) {
    if (ctx.seen.indexOf(value[key]) < 0) {
      if (recurseTimes === null) {
        str = formatValue(ctx, value[key], null);
      } else {
        str = formatValue(ctx, value[key], recurseTimes - 1);
      }
      if (str.indexOf('\n') > -1) {
        if (array) {
          str = str.split('\n').map(function(line) {
            return '  ' + line;
          }).join('\n').substr(2);
        } else {
          str = '\n' + str.split('\n').map(function(line) {
            return '   ' + line;
          }).join('\n');
        }
      }
    } else {
      str = ctx.stylize('[Circular]', 'special');
    }
  }
  if (typeof name === 'undefined') {
    if (array && key.match(/^\d+$/)) {
      return str;
    }
    name = JSON.stringify('' + key);
    if (name.match(/^"([a-zA-Z_][a-zA-Z_0-9]*)"$/)) {
      name = name.substr(1, name.length - 2);
      name = ctx.stylize(name, 'name');
    } else {
      name = name.replace(/'/g, "\\'")
                 .replace(/\\"/g, '"')
                 .replace(/(^"|"$)/g, "'");
      name = ctx.stylize(name, 'string');
    }
  }

  return name + ': ' + str;
}

function reduceToSingleString(output, base, braces) {
  var length = output.reduce(function(prev, cur) {
    return prev + cur.length + 1;
  }, 0);

  if (length > 60) {
    return braces[0] +
           (base === '' ? '' : base + '\n ') +
           ' ' +
           output.join(',\n  ') +
           ' ' +
           braces[1];
  }

  return braces[0] + base + ' ' + output.join(', ') + ' ' + braces[1];
}

function isTypedArray(ar) {
  // Unfortunately there's no way to check if an object is a TypedArray
  // We have to check if it's one of these types
  return (typeof ar === 'object' && /\w+Array]$/.test(objectToString(ar)));
}

function isArray(ar) {
  return Array.isArray(ar) ||
         (typeof ar === 'object' && objectToString(ar) === '[object Array]');
}

function isRegExp(re) {
  return typeof re === 'object' && objectToString(re) === '[object RegExp]';
}

function isDate(d) {
  return typeof d === 'object' && objectToString(d) === '[object Date]';
}

function isError(e) {
  return typeof e === 'object' && objectToString(e) === '[object Error]';
}

function objectToString(o) {
  return Object.prototype.toString.call(o);
}