Module util

Common tool module

Object

LruCache

LRU (least recently used) cache object, see LruCache Object.

1LruCache util.LruCache;

Static function

format

Format variables according to the specified format

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static String util.format(String fmt,
    ...args);

Call parameters:

fmt: String, format string
args: ..., optional parameter list

Return result:

String, Returns the formatted string

Formatting variables

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static String util.format(...args);

Call parameters:

args: ..., optional parameter list

Return result:

String, Returns the formatted string

inherits

Inherit the prototype function from one constructor to another. The prototype of the constructor will be set to a new object created from the superConstructor.

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static util.inherits(Value constructor,
    Value superConstructor);

Call parameters:

constructor: Value, the initial constructor
superConstructor: Value, the superclass to be inherited

inspect

The function returns the string representation of obj, which is mainly used for debugging. Additional options can be used to change certain aspects of the format string.

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static String util.inspect(Value obj,
    Object options = {});

Call parameters:

obj: Value, specify the object to be processed
options: Object, specify format control options

Return result:

String, Returns the formatted string

The following parameters are supported:

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    "colors": false, // 指定是否输出 ansi 作色字符串，缺省为 false
    "table": false, // 指定输出 table 格式，缺省为 false
    "encode_string": true, // 指定表格中的字符串是否编码，缺省为 true
    "fields": [], // 当 table 为 true 时指定显示字段
}

deprecate

Encapsulate the given function, this function is only compatible, and does not output a warning

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static Function util.deprecate(Function fn,
    String msg,
    String code = "");

Call parameters:

fn: Function, given the function to be encapsulated
msg: String, given warning message
code: String, given warning number

Return result:

Function, If the encapsulation result

isEmpty

Check whether the given variable does not contain any value (no enumerable attributes)

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static Boolean util.isEmpty(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is empty

isArray

Check whether the given variable is an array

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static Boolean util.isArray(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Returns True if it is an array

isBoolean

Check whether the given variable is Boolean

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static Boolean util.isBoolean(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is Boolean

isNull

Check whether the given variable is Null

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static Boolean util.isNull(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is Null

isNullOrUndefined

Check whether the given variable is Null or Undefined

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static Boolean util.isNullOrUndefined(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is Null or Undefined

isNumber

Check whether the given variable is a number

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static Boolean util.isNumber(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is a number

isBigInt

Check whether the given variable is BigInt

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static Boolean util.isBigInt(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is a number

isString

Check whether the given variable is a string

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static Boolean util.isString(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Returns True if it is a string

isUndefined

Check whether the given variable is Undefined

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static Boolean util.isUndefined(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is Undefined

isRegExp

Check whether the given variable is a regular object

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static Boolean util.isRegExp(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is a regular object

isObject

Check whether the given variable is an object

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static Boolean util.isObject(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is an object

isDate

Check whether the given variable is a date object

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static Boolean util.isDate(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is a date object

isNativeError

Check whether the given variable is the wrong object

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static Boolean util.isNativeError(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is an error object

isPrimitive

Check whether the given variable is of primitive type

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static Boolean util.isPrimitive(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is a primitive type

isSymbol

Check whether the given variable is of type Symbol

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static Boolean util.isSymbol(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, If it is a Symbol type, it returns True

isDataView

Check whether the given variable is of type DataView

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static Boolean util.isDataView(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is of DataView type

isExternal

Check whether the given variable is of type External

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static Boolean util.isExternal(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, If it is an External type, it returns True

isMap

Check whether the given variable is of type Map

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static Boolean util.isMap(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is a Map type

isMapIterator

Check whether the given variable is of type MapIterator

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static Boolean util.isMapIterator(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is of MapIterator type

isPromise

Check whether the given variable is of Promise type

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static Boolean util.isPromise(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is a Promise type

isAsyncFunction

Check whether the given variable is of type AsyncFunction

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static Boolean util.isAsyncFunction(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is of type AsyncFunction

isSet

Check whether the given variable is of type Set

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static Boolean util.isSet(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, If it is a Set type, it returns True

isSetIterator

Check whether the given variable is of type SetIterator

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static Boolean util.isSetIterator(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Return True if it is of SetIterator type

isTypedArray

Check whether the given variable is of TypedArray type

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static Boolean util.isTypedArray(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, If it is a TypedArray type, it returns True

isUint8Array

Check whether the given variable is of type Uint8Array

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static Boolean util.isUint8Array(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Returns True if it is of Uint8Array type

isFunction

Check whether the given variable is a function object

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static Boolean util.isFunction(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, Returns True if it is a function object

isBuffer

Check whether the given variable is a function Buffer Object

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static Boolean util.isBuffer(Value v);

Call parameters:

v: Value, given the variable to be tested

Return result:

Boolean, If it is a function Buffer Object returns True

isDeepEqual

The depth of the test value is equal to the expected value

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static Boolean util.isDeepEqual(Value actual,
    Value expected);

Call parameters:

actual: Value, the value to be tested
expected: Value, expected value

Return result:

Boolean, Return True if the depths are equal

has

Query whether the specified object contains the given key

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static Boolean util.has(Value v,
    String key);

Call parameters:

v: Value, given the object to be queried
key: String, specify the key to be queried

Return result:

Boolean, Returns an array of all keys of the object

keys

Query all key arrays of the specified object

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static Array util.keys(Value v);

Call parameters:

v: Value, given the object to be queried

Return result:

Array, Returns an array of all keys of the object

values

Query the array of all values of the specified object

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static Array util.values(Value v);

Call parameters:

v: Value, given the object to be queried

Return result:

Array, Returns an array of all values of the object

clone

Clone the given variable, if it is an object or an array, copy the content to the new object

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static Value util.clone(Value v);

Call parameters:

v: Value, given the variable to be cloned

Return result:

Value, Return the cloned result

deepFreeze

Deep freeze an object, the frozen object and its contained objects will not be allowed to be modified

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static util.deepFreeze(Value v);

Call parameters:

v: Value, specify the object to be frozen

extend

Extend the key value of one or more objects to the specified object

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static Value util.extend(Value v,
    ...objs);

Call parameters:

v: Value, specify the object to be expanded
objs: ..., specify one or more objects for expansion

Return result:

Value, Returns the expanded result

_extend

Extend the key value of one or more objects to the specified object, which is an alias of extend

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static Value util._extend(Value v,
    ...objs);

Call parameters:

v: Value, specify the object to be expanded
objs: ..., specify one or more objects for expansion

Return result:

Value, Returns the expanded result

pick

Return aobjectCopy, only filter out the attribute value of the specified key

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static Object util.pick(Value v,
    ...objs);

Call parameters:

v: Value, specify the object to be filtered
objs: ..., specify one or more keys for selection

Return result:

Object, Return the filtered result

omit

Return aobjectCopy, just exclude the attribute value of the specified key

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static Object util.omit(Value v,
    ...keys);

Call parameters:

v: Value, specify the object to be filtered
keys: ..., specify one or more keys to exclude

Return result:

Object, Returns excluded results

first

Get the first element of the array

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static Value util.first(Value v);

Call parameters:

v: Value, given the array to be obtained

Return result:

Value, Return the retrieved element

Get the first multiple elements of the array

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static Value util.first(Value v,
    Integer n);

Call parameters:

v: Value, given the array to be obtained
n: Integer, specify the number of elements to be obtained

Return result:

Value, Returns the obtained element array

last

Get the first element of the array

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static Value util.last(Value v);

Call parameters:

v: Value, given the array to be obtained

Return result:

Value, Return the retrieved element

Get multiple elements at the end of the array

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static Value util.last(Value v,
    Integer n);

Call parameters:

v: Value, given the array to be obtained
n: Integer, specify the number of elements to be obtained

Return result:

Value, Returns the obtained element array

unique

Get a copy of the elements of the array after de-duplication

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static Array util.unique(Value v,
    Boolean sorted = false);

Call parameters:

v: Value, given the array to be deduplicated
sorted: Boolean, specify whether the array is sorted or not, if the array is specified to be sorted, a fast algorithm will be used

Return result:

Array, Return the array after removing duplicate elements

union

Combine the values of one or more arrays into an array with unique values

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static Array util.union(...arrs);

Call parameters:

arrs: ..., specify one or more arrays for merging

Return result:

Array, Return the merged result

intersection

Returns the intersection of an array containing arr and excluding one or more array elements

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static Array util.intersection(...arrs);

Call parameters:

arrs: ..., specify one or more arrays for computing intersection

Return result:

Array, Returns the result of computing the intersection

flatten

Convert an array with multiple levels of nesting (the nesting can be any number of levels) into an array with only one level. If you pass the shallow parameter, the array will only reduce one-dimensional nesting.

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static Array util.flatten(Value arr,
    Boolean shallow = false);

Call parameters:

arr: Value, specify the array to be converted
shallow: Boolean, specify whether to reduce only one-dimensional nesting, the default is false

Return result:

Array, Return the result of the conversion

without

Returns an array containing one or more elements excluded from the arr array

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static Array util.without(Value arr,
    ...els);

Call parameters:

arr: Value, specify the array to be excluded
els: ..., specify one or more elements to exclude

Return result:

Array, Returns excluded results

difference

Return an array that contains the arr array and excludes the without array element

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static Array util.difference(Array list,
    ...arrs);

Call parameters:

list: Array, specify the array to be excluded
arrs: ..., specify one or more arrays to exclude

Return result:

Array, Returns excluded results

each

Traverse all the elements in the list, and output each element in order with traversal. If the context parameter is passed, the iterator is bound to the context object. Each call to iterator will pass three parameters: (element, index, list)

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static Value util.each(Value list,
    Function iterator,
    Value context = undefined);

Call parameters:

list: Value, specify the list or object to be traversed
iterator: Function, specify the callback function used for traversal
context: Value, specify the context object bound when calling iterator

Return result:

Value, Return the list itself

map

Through the transformation function (iterator), each value in the list is mapped to a new array. If the context parameter is passed, the iterator is bound to the context object. Each call to iterator will pass three parameters: (element, index, list)

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static Array util.map(Value list,
    Function iterator,
    Value context = undefined);

Call parameters:

list: Value, specify the list or object to be transformed
iterator: Function, specify the callback function used for transformation
context: Value, specify the context object bound when calling iterator

Return result:

Array, Returns the result of the transformation

reduce

Reduce the elements in the list to a single value. If the context parameter is passed, the iterator is bound to the context object. Each call to iterator will pass three parameters: (memo, element, index, list)

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static Value util.reduce(Value list,
    Function iterator,
    Value memo,
    Value context = undefined);

Call parameters:

list: Value, specify the list or object to be resolved
iterator: Function, specify the callback function used for resolution
memo: Value, specify the initial value of resolution
context: Value, specify the context object bound when calling iterator

Return result:

Value, Return the result of resolution

parseArgs

Parse the command line string and return the parameter list

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static NArray util.parseArgs(String command);

Call parameters:

command: String, specify the command line string to be parsed

Return result:

NArray, Return the parsed parameter list

compile

Compile script as binary code

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static Buffer util.compile(String srcname,
    String script,
    Integer mode = 0);

Call parameters:

srcname: String, specify the name of the script to be added
script: String, specify the script code to be compiled
mode: Integer, compilation mode, 0: module, 1: script, 2: worker, the default is 0

Return result:

Buffer, Return the compiled binary code

util.compileThe script can be compiled into v8 internal running data block (non-machine execution code). After the compiled code is saved as *.jsc, it can be loaded and executed directly by run and require.

After compilation, the target code will not be able to obtain the source code in reverse, and the program that depends on Function.toString will not run normally.

sync

Wrap callback or async functions as synchronous calls

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static Function util.sync(Function func,
    Boolean async_func = false);

Call parameters:

func: Function, given the function to be wrapped
async_func: Boolean, specify to process func as async function, if it is false, it will be judged automatically

Return result:

Function, Returns the function that runs synchronously

util.sync Treat the callback function or async function as a sync function for easy calling.

The callback example is as follows:

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// callback
var util = require('util');

function cb_test(a, b, cb) {
    setTimeout(() => {
        cb(null, a + b);
    }, 100);
}

var fn_sync = util.sync(cb_test);
console.log(fn_sync(100, 200));

The async example is as follows:

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// async/await
var util = require('util');

async function async_test(a, b) {
    return a + b;
}

var fn_sync = util.sync(async_test);
console.log(fn_sync(100, 200));

For functions that return promises that are not marked as async, you can manually specify the sync mode:

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// async/await
var util = require('util');

function async_test(a, b) {
    return new Promise(function(resolve, reject) {
        resolve(a + b);
    });
}

var fn_sync = util.sync(async_test, true);
console.log(fn_sync(100, 200));

promisify

Wrap the callback function as async call

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static Function util.promisify(Function func);

Call parameters:

func: Function, given the function to be wrapped

Return result:

Function, Return the async function

util.promisify Treat the callback function as an async function for easy calling.

The callback example is as follows:

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// callback
var util = require('util');

function cb_test(a, b, cb) {
    setTimeout(() => {
        cb(null, a + b);
    }, 100);
}

var fn_sync = util.promisify(cb_test);
console.log(async fn_sync(100, 200));

callbackify

Wrap the async function as a callback call

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static Function util.callbackify(Function func);

Call parameters:

func: Function, given the function to be wrapped

Return result:

Function, Return callback function

util.callbackify Treat the async function as a callback function for easy calling.

The async example is as follows:

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// async
var util = require('util');

async function async_test(a, b) {
    return a + b;
}

var fn_callback = util.callbackify(async_test);

fn_callback(100, 200, (err, result) => {
    console.log(result);
});

buildInfo

Query current engine and component version information

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static Object util.buildInfo();

Return result:

Object, Returns the component version object

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24{
    "fibjs": "0.25.0",
    "clang": "9.1",
    "date": "Jun 12 2018 07:22:40",
    "vender": {
        "ev": "4.24",
        "expat": "2.2.5",
        "gd": "2.2.4",
        "jpeg": "8.3",
        "leveldb": "1.17",
        "mongo": "0.7",
        "pcre": "8.21",
        "png": "1.5.4",
        "mbedtls": "2.6.1",
        "snappy": "1.1.2",
        "sqlite": "3.23.0",
        "tiff": "3.9.5",
        "uuid": "1.6.2",
        "v8": "6.7.288.20",
        "v8-snapshot": true,
        "zlib": "1.2.7",
        "zmq": "3.1"
    }
}

Development Guide

Basic module

Built-in objects

Community module

Module util

Object

LruCache

Static function

format

inherits

inspect

deprecate

isEmpty

isArray

isBoolean

isNull

isNullOrUndefined

isNumber

isBigInt

isString

isUndefined

isRegExp

isObject

isDate

isNativeError

isPrimitive

isSymbol

isDataView

isExternal

isMap

isMapIterator

isPromise

isAsyncFunction

isSet

isSetIterator

isTypedArray

isUint8Array

isFunction

isBuffer

isDeepEqual

has

keys

values

clone

deepFreeze

extend

_extend

pick

omit

first

last

unique

union

intersection

flatten

without

difference

each

map

reduce

parseArgs

compile

sync

promisify

callbackify

buildInfo