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This module provides miscellaneous facilities for working with strings, numbers, dates, and objects and arrays of these basic types.
Creates a deep copy of a primitive type, object, or array of primitive types.
Returns whether two objects are equal.
Returns true if the given object has no properties and false otherwise. This
is O(1) (unlike Object.keys(obj).length === 0
, which is O(N)).
Returns true if the given object has an enumerable, non-inherited property
called key
. For information on enumerability and ownership of properties, see
the MDN
documentation.
Like Array.forEach, but iterates enumerable, owned properties of an object rather than elements of an array. Equivalent to:
for (var key in obj) {
if (Object.prototype.hasOwnProperty.call(obj, key)) {
callback(key, obj[key]);
}
}
Flattens an object up to a given level of nesting, returning an array of arrays of length “depth + 1”, where the first “depth” elements correspond to flattened columns and the last element contains the remaining object . For example:
flattenObject({
'I': {
'A': {
'i': {
'datum1': [ 1, 2 ],
'datum2': [ 3, 4 ]
},
'ii': {
'datum1': [ 3, 4 ]
}
},
'B': {
'i': {
'datum1': [ 5, 6 ]
},
'ii': {
'datum1': [ 7, 8 ],
'datum2': [ 3, 4 ],
},
'iii': {
}
}
},
'II': {
'A': {
'i': {
'datum1': [ 1, 2 ],
'datum2': [ 3, 4 ]
}
}
}
}, 3)
becomes:
[
[ 'I', 'A', 'i', { 'datum1': [ 1, 2 ], 'datum2': [ 3, 4 ] } ],
[ 'I', 'A', 'ii', { 'datum1': [ 3, 4 ] } ],
[ 'I', 'B', 'i', { 'datum1': [ 5, 6 ] } ],
[ 'I', 'B', 'ii', { 'datum1': [ 7, 8 ], 'datum2': [ 3, 4 ] } ],
[ 'I', 'B', 'iii', {} ],
[ 'II', 'A', 'i', { 'datum1': [ 1, 2 ], 'datum2': [ 3, 4 ] } ]
]
This function is strict: “depth” must be a non-negative integer and “obj” must be a non-null object with at least “depth” levels of nesting under all keys.
This is similar to flattenObject
except that instead of returning an array,
this function invokes func(entry)
for each entry
in the array that
flattenObject
would return. flattenIter(obj, depth, func)
is logically
equivalent to flattenObject(obj, depth).forEach(func)
. Importantly, this
version never constructs the full array. Its memory usage is O(depth) rather
than O(n) (where n
is the number of flattened elements).
There’s another difference between flattenObject
and flattenIter
that’s
related to the special case where depth === 0
. In this case, flattenObject
omits the array wrapping obj
(which is regrettable).
Fetch nested property “key” from object “obj”, traversing objects as needed.
For example, pluck(obj, "foo.bar.baz")
is roughly equivalent to
obj.foo.bar.baz
, except that:
pluck({}, "foo.bar")
is just undefined.pluck({ 'foo.bar': 1 }, 'foo.bar')
is 1, not undefined. This is also
true recursively, so pluck({ 'a': { 'foo.bar': 1 } }, 'a.foo.bar')
is
also 1, not undefined.Returns an element from “array” selected uniformly at random. If “array” is empty, throws an Error.
Returns true if the given string starts with the given prefix and false otherwise.
Returns true if the given string ends with the given suffix and false otherwise.
Parses the contents of str
(a string) as an integer. On success, the integer
value is returned (as a number). On failure, an error is returned describing
why parsing failed.
By default, leading and trailing whitespace characters are not allowed, nor are
trailing characters that are not part of the numeric representation. This
behaviour can be toggled by using the options below. The empty string (''
) is
not considered valid input. If the return value cannot be precisely represented
as a number (i.e., is smaller than Number.MIN_SAFE_INTEGER
or larger than
Number.MAX_SAFE_INTEGER
), an error is returned. Additionally, the string
'-0'
will be parsed as the integer 0
, instead of as the IEEE floating point
value -0
.
This function accepts both upper and lowercase characters for digits, similar to
parseInt()
, Number()
, and strtol(3C).
The following may be specified in options
:
Option | Type | Default | Meaning |
---|---|---|---|
base | number | 10 | numeric base (radix) to use, in the range 2 to 36 |
allowSign | boolean | true | whether to interpret any leading + (positive) and - (negative) characters |
allowImprecise | boolean | false | whether to accept values that may have lost precision (past MAX_SAFE_INTEGER or below MIN_SAFE_INTEGER ) |
allowPrefix | boolean | false | whether to interpret the prefixes 0b (base 2), 0o (base 8), 0t (base 10), or 0x (base 16) |
allowTrailing | boolean | false | whether to ignore trailing characters |
trimWhitespace | boolean | false | whether to trim any leading or trailing whitespace/line terminators |
leadingZeroIsOctal | boolean | false | whether a leading zero indicates octal |
Note that if base
is unspecified, and allowPrefix
or leadingZeroIsOctal
are, then the leading characters can change the default base from 10. If base
is explicitly specified and allowPrefix
is true, then the prefix will only be
accepted if it matches the specified base. base
and leadingZeroIsOctal
cannot be used together.
Context: It’s tricky to parse integers with JavaScript’s built-in facilities for several reasons:
parseInt()
and Number()
by default allow the base to be specified in the
input string by a prefix (e.g., 0x
for hex).parseInt()
allows trailing nonnumeric characters.Number(str)
returns 0 when str
is the empty string (''
).parseInt('9007199254740993')
returns 9007199254.-
and +
signs before the digit.While each of these may be desirable in some contexts, there are also times when
none of them are wanted. parseInteger()
grants greater control over what
input’s permissible.
Converts a Date object to an ISO8601 date string of the form “YYYY-MM-DDTHH:MM:SS.sssZ”. This format is not customizable.
Parses a date expressed as a string, as either a number of milliseconds since the epoch or any string format that Date accepts, giving preference to the former where these two sets overlap (e.g., strings containing small numbers).
Given two hrtime readings (as from Node’s process.hrtime()
), where timeA is
later than timeB, compute the difference and return that as an hrtime. It is
illegal to invoke this for a pair of times where timeB is newer than timeA.
Add two hrtime intervals (as from Node’s process.hrtime()
), returning a new
hrtime interval array. This function does not modify either input argument.
Add two hrtime intervals (as from Node’s process.hrtime()
), storing the
result in timeA
. This function overwrites (and returns) the first argument
passed in.
This suite of functions converts a hrtime interval (as from Node’s
process.hrtime()
) into a scalar number of nanoseconds, microseconds or
milliseconds. Results are truncated, as with Math.floor()
.
Uses JSON validation (via JSV) to validate the given object against the given schema. On success, returns null. On failure, returns (does not throw) a useful Error object.
Check an object for unexpected properties. Accepts the object to check, and an array of allowed property name strings. If extra properties are detected, an array of extra property names is returned. If no properties other than those in the allowed list are present on the object, the returned array will be of zero length.
Merge properties from objects “provided”, “overrides”, and “defaults”. The intended use case is for functions that accept named arguments in an “args” object, but want to provide some default values and override other values. In that case, “provided” is what the caller specified, “overrides” are what the function wants to override, and “defaults” contains default values.
The function starts with the values in “defaults”, overrides them with the values in “provided”, and then overrides those with the values in “overrides”. For convenience, any of these objects may be falsey, in which case they will be ignored. The input objects are never modified, but properties in the returned object are not deep-copied.
For example:
mergeObjects(undefined, { 'objectMode': true }, { 'highWaterMark': 0 })
returns:
{ 'objectMode': true, 'highWaterMark': 0 }
For another example:
mergeObjects(
{ 'highWaterMark': 16, 'objectMode': 7 }, /* from caller */
{ 'objectMode': true }, /* overrides */
{ 'highWaterMark': 0 }); /* default */
returns:
{ 'objectMode': true, 'highWaterMark': 16 }
See separate contribution guidelines.