mirror of
https://github.com/1disk/edp445.git
synced 2024-08-14 22:47:02 +00:00
287 lines
10 KiB
Markdown
287 lines
10 KiB
Markdown
# jsprim: utilities for primitive JavaScript types
|
|
|
|
This module provides miscellaneous facilities for working with strings,
|
|
numbers, dates, and objects and arrays of these basic types.
|
|
|
|
|
|
### deepCopy(obj)
|
|
|
|
Creates a deep copy of a primitive type, object, or array of primitive types.
|
|
|
|
|
|
### deepEqual(obj1, obj2)
|
|
|
|
Returns whether two objects are equal.
|
|
|
|
|
|
### isEmpty(obj)
|
|
|
|
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)).
|
|
|
|
### hasKey(obj, key)
|
|
|
|
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.](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Enumerability_and_ownership_of_properties)
|
|
|
|
### forEachKey(obj, callback)
|
|
|
|
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]);
|
|
}
|
|
}
|
|
|
|
|
|
### flattenObject(obj, depth)
|
|
|
|
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.
|
|
|
|
|
|
### flattenIter(obj, depth, func)
|
|
|
|
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).
|
|
|
|
|
|
### pluck(obj, key)
|
|
|
|
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:
|
|
|
|
1. If traversal fails, the resulting value is undefined, and no error is
|
|
thrown. For example, `pluck({}, "foo.bar")` is just undefined.
|
|
2. If "obj" has property "key" directly (without traversing), the
|
|
corresponding property is returned. For example,
|
|
`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.
|
|
|
|
|
|
### randElt(array)
|
|
|
|
Returns an element from "array" selected uniformly at random. If "array" is
|
|
empty, throws an Error.
|
|
|
|
|
|
### startsWith(str, prefix)
|
|
|
|
Returns true if the given string starts with the given prefix and false
|
|
otherwise.
|
|
|
|
|
|
### endsWith(str, suffix)
|
|
|
|
Returns true if the given string ends with the given suffix and false
|
|
otherwise.
|
|
|
|
|
|
### parseInteger(str, options)
|
|
|
|
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)](https://illumos.org/man/3C/strtol).
|
|
|
|
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 (`''`).
|
|
- Both functions return incorrect values when the input string represents a
|
|
valid integer outside the range of integers that can be represented precisely.
|
|
Specifically, `parseInt('9007199254740993')` returns 9007199254740992.
|
|
- Both functions always accept `-` and `+` signs before the digit.
|
|
- Some older JavaScript engines always interpret a leading 0 as indicating
|
|
octal, which can be surprising when parsing input from users who expect a
|
|
leading zero to be insignificant.
|
|
|
|
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.
|
|
|
|
### iso8601(date)
|
|
|
|
Converts a Date object to an ISO8601 date string of the form
|
|
"YYYY-MM-DDTHH:MM:SS.sssZ". This format is not customizable.
|
|
|
|
|
|
### parseDateTime(str)
|
|
|
|
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).
|
|
|
|
|
|
### hrtimeDiff(timeA, timeB)
|
|
|
|
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.
|
|
|
|
### hrtimeAdd(timeA, timeB)
|
|
|
|
Add two hrtime intervals (as from Node's `process.hrtime()`), returning a new
|
|
hrtime interval array. This function does not modify either input argument.
|
|
|
|
|
|
### hrtimeAccum(timeA, timeB)
|
|
|
|
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.
|
|
|
|
|
|
### hrtimeNanosec(timeA), hrtimeMicrosec(timeA), hrtimeMillisec(timeA)
|
|
|
|
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()`.
|
|
|
|
|
|
### validateJsonObject(schema, object)
|
|
|
|
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.
|
|
|
|
|
|
### extraProperties(object, allowed)
|
|
|
|
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.
|
|
|
|
### mergeObjects(provided, overrides, defaults)
|
|
|
|
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 }
|
|
|
|
|
|
# Contributing
|
|
|
|
See separate [contribution guidelines](CONTRIBUTING.md).
|