How to use the util.isDate function in util

docs.forEach(function (doc) {
        contents.push({ doc: JSON.stringify(doc, undefined, 2)
                      , _id: util.isDate(doc._id) ? doc._id.toISOString() : doc._id });   // The "edit" page needs to be given Date-type _ids in ISO format or it won't find them
      });

function areThingsEqual (a, b) {
  var aKeys , bKeys , i;

  // Strings, booleans, numbers, null
  if (a === null || typeof a === 'string' || typeof a === 'boolean' || typeof a === 'number' ||
      b === null || typeof b === 'string' || typeof b === 'boolean' || typeof b === 'number') { return a === b; }

  // Dates
  if (util.isDate(a) || util.isDate(b)) { return util.isDate(a) && util.isDate(b) && a.getTime() === b.getTime(); }

  // Arrays (no match since arrays are used as a $in)
  // undefined (no match since they mean field doesn't exist and can't be serialized)
  if (util.isArray(a) || util.isArray(b) || a === undefined || b === undefined) { return false; }

  // General objects (check for deep equality)
  // a and b should be objects at this point
  try {
    aKeys = Object.keys(a);
    bKeys = Object.keys(b);
  } catch (e) {
    return false;
  }

  if (aKeys.length !== bKeys.length) { return false; }
  for (i = 0; i < aKeys.length; i += 1) {

return typeof a === 'string' ? compareStrings(a, b) : 1;
  }

  // Booleans
  if (typeof a === 'boolean') {
    return typeof b === 'boolean' ? compareNSB(a, b) : -1;
  }
  if (typeof b === 'boolean') {
    return typeof a === 'boolean' ? compareNSB(a, b) : 1;
  }

  // Dates
  if (util.isDate(a)) {
    return util.isDate(b) ? compareNSB(a.getTime(), b.getTime()) : -1;
  }
  if (util.isDate(b)) {
    return util.isDate(a) ? compareNSB(a.getTime(), b.getTime()) : 1;
  }

  // Arrays (first element is most significant and so on)
  if (util.isArray(a)) {
    return util.isArray(b) ? compareArrays(a, b) : -1;
  }
  if (util.isArray(b)) {
    return util.isArray(a) ? compareArrays(a, b) : 1;
  }

  // Objects
  aKeys = Object.keys(a).sort();
  bKeys = Object.keys(b).sort();

  for (i = 0; i < Math.min(aKeys.length, bKeys.length); i += 1) {

function areThingsEqual (a, b) {
  var aKeys , bKeys , i;

  // Strings, booleans, numbers, null
  if (a === null || typeof a === 'string' || typeof a === 'boolean' || typeof a === 'number' ||
      b === null || typeof b === 'string' || typeof b === 'boolean' || typeof b === 'number') { return a === b; }

  // Dates
  if (util.isDate(a) || util.isDate(b)) { return util.isDate(a) && util.isDate(b) && a.getTime() === b.getTime(); }

  // Arrays (no match since arrays are used as a $in)
  // undefined (no match since they mean field doesn't exist and can't be serialized)
  if (util.isArray(a) || util.isArray(b) || a === undefined || b === undefined) { return false; }

  // General objects (check for deep equality)
  // a and b should be objects at this point
  try {
    aKeys = Object.keys(a);
    bKeys = Object.keys(b);
  } catch (e) {
    return false;
  }

  if (aKeys.length !== bKeys.length) { return false; }
  for (i = 0; i < aKeys.length; i += 1) {

function _deepEqual(actual, expected, strict) {
  // 7.1. All identical values are equivalent, as determined by ===.
  if (actual === expected) {
    return true;
  } else if (actual instanceof Buffer && expected instanceof Buffer) {
    return compare(actual, expected) === 0;

  // 7.2. If the expected value is a Date object, the actual value is
  // equivalent if it is also a Date object that refers to the same time.
  } else if (util.isDate(actual) && util.isDate(expected)) {
    return actual.getTime() === expected.getTime();

  // 7.3 If the expected value is a RegExp object, the actual value is
  // equivalent if it is also a RegExp object with the same source and
  // properties (`global`, `multiline`, `lastIndex`, `ignoreCase`).
  } else if (util.isRegExp(actual) && util.isRegExp(expected)) {
    return actual.source === expected.source &&
           actual.global === expected.global &&
           actual.multiline === expected.multiline &&
           actual.lastIndex === expected.lastIndex &&
           actual.ignoreCase === expected.ignoreCase;

  // 7.4. Other pairs that do not both pass typeof value == 'object',
  // equivalence is determined by ==.
  } else if ((actual === null || typeof actual !== 'object') &&
             (expected === null || typeof expected !== 'object')) {

// 7.1. All identical values are equivalent, as determined by ===.
  if (actual === expected) {
    return true;

  } else if (util.isBuffer(actual) && util.isBuffer(expected)) {
    if (actual.length != expected.length) return false;

    for (var i = 0; i < actual.length; i++) {
      if (actual[i] !== expected[i]) return false;
    }

    return true;

  // 7.2. If the expected value is a Date object, the actual value is
  // equivalent if it is also a Date object that refers to the same time.
  } else if (util.isDate(actual) && util.isDate(expected)) {
    return actual.getTime() === expected.getTime();

  // 7.3 If the expected value is a RegExp object, the actual value is
  // equivalent if it is also a RegExp object with the same source and
  // properties (`global`, `multiline`, `lastIndex`, `ignoreCase`).
  } else if (util.isRegExp(actual) && util.isRegExp(expected)) {
    return actual.source === expected.source &&
           actual.global === expected.global &&
           actual.multiline === expected.multiline &&
           actual.lastIndex === expected.lastIndex &&
           actual.ignoreCase === expected.ignoreCase;

  // 7.4. Other pairs that do not both pass typeof value == 'object',
  // equivalence is determined by ==.
  } else if (!util.isObject(actual) && !util.isObject(expected)) {
    return actual == expected;

function toUnixTimestamp(time) {
  // eslint-disable-next-line eqeqeq
  if (typeof time === 'string' && +time == time) {
    return +time;
  }
  if (Number.isFinite(time)) {
    if (time < 0) {
      return Date.now() / 1000;
    }
    return time;
  }
  if (util.isDate(time)) {
    // convert to 123.456 UNIX timestamp
    return time.getTime() / 1000;
  }
  throw new Error('Cannot parse time: ' + time);
}

ofType: function (a, e) {
    var type = typeof a;
//#JSCOVERAGE_IF typeof /a/ === 'function'
    // webkit (incorrectly?) reports regexes as functions. Normalize this to 'object'.
    if (type === 'function' && a.constructor === RegExp) {
      type = 'object';
    }
//#JSCOVERAGE_ENDIF
    switch (e.toLowerCase()) {
    case 'array' :
      return util.isArray(a);
    case 'date' :
      return util.isDate(a);
    case 'regexp' :
      return util.isRegExp(a);
    default :
      return type === e;
    }
  },
  matches: function (a, m) {

value: function (v) {
    if (v === null) {
      return null;
    } else if (typeof v === 'string' || typeof v === 'number' || typeof v === 'boolean' || v instanceof ObjectID) {
      return v;
    } else if (util.isDate(v)) {
      return moment(v).utc().format('YYYY-MM-DD HH:mm:ss');
    } else if (util.isArray(v)) {
      if (v.length === 0) {
        return v;
      } else {
        return v.map(function (item) {
          return GCP.BigQueryTable.value(item);
        }).filter(function (item) {
          return item !== null;
        });
      }
    } else {
      return JSON.stringify(v);
    }
  },

function isPrimitiveType (obj) {
  return ( typeof obj === 'boolean' ||
       typeof obj === 'number' ||
       typeof obj === 'string' ||
       obj === null ||
       util.isDate(obj) ||
       util.isArray(obj));
}