Object built-in object

Object LevelDB

LevelDB database objects

Used to create and manage dictionary objects, the creation method:

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var db = require("db"); var test = new db.openLevelDB("test.db");

Inheritance

#lineWidth: 1.5 #font: Helvetica,sans-Serif #fontSize: 10 #leading: 1.6 #.this: fill=lightgray #.class: fill=white [<class>object|toString();toJSON()] [<this>LevelDB|has();get();mget();set();mset();mremove();remove();forEach();between();begin();commit();close()] [object] <:- [LevelDB] object toString() toJSON() LevelDB has() get() mget() set() mset() mremove() remove() forEach() between() begin() commit() close()

Member function

has

Check whether there is data with the specified key value in the database

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Boolean LevelDB.has(Buffer key) async;

Call parameters:

  • key: Buffer, Specify the key value to be checked

Return result:

  • Boolean, Returns whether the key value exists

get

Query the value of the specified key

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Buffer LevelDB.get(Buffer key) async;

Call parameters:

  • key: Buffer, Specify the key value to be queried

Return result:

  • Buffer, Returns the value corresponding to the key value, if it does not exist, returns null

mget

Query a set of specified key values

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NArray LevelDB.mget(Array keys);

Call parameters:

  • keys: Array, specify the key value array to be queried

Return result:

  • NArray, Returns an array containing key values

set

Set a key value data, insert new data if the key value does not exist

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LevelDB.set(Buffer key, Buffer value) async;

Call parameters:

  • key: Buffer, Specify the key value to be set
  • value: Buffer, Specify the data to be set

mset

Set a set of key-value data, insert new data if the key-value does not exist

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LevelDB.mset(Object map);

Call parameters:

  • map: Object, specify the key-value data dictionary to be set

mremove

Delete a set of specified key values

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LevelDB.mremove(Array keys);

Call parameters:

  • keys: Array, specify the key value array to be deleted

remove

Delete all values ​​of the specified key value

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LevelDB.remove(Buffer key) async;

Call parameters:

  • key: Buffer, Specify the key value to be deleted

forEach

Enumerate all key-value pairs in the database

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LevelDB.forEach(Function func);

Call parameters:

  • func: Function, enumeration callback function

The callback function has two parameters, (value, key)

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var db = require("db"); var test = new db.openLevelDB("test.db"); test.forEach(function(value, key) { ... });

between

Enumerate the key-value pairs between from and to in the database

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LevelDB.between(Buffer from, Buffer to, Function func);

Call parameters:

  • from: Buffer, The minimum key value of the enumeration, this key value is included in the enumeration
  • to: Buffer, The maximum key value of the enumeration, this key value is not included in the enumeration
  • func: Function, enumeration callback function

The callback function has two parameters, (value, key)

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var db = require("db"); var test = new db.openLevelDB("test.db"); test.between("aaa", "bbb", function(value, key) { ... });

begin

Start a transaction on the current database

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LevelDB LevelDB.begin();

Return result:

  • LevelDB, Return an open transaction object

commit

Commit the current transaction

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LevelDB.commit();

close

Close the current database connection or transaction

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LevelDB.close() async;

toString

Returns the string representation of the object, generally returns "[Native Object]", the object can be re-implemented according to its own characteristics

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String LevelDB.toString();

Return result:

  • String, Returns the string representation of the object

toJSON

Returns the JSON format representation of the object, generally returns a collection of readable attributes defined by the object

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Value LevelDB.toJSON(String key = "");

Call parameters:

  • key: String, unused

Return result:

  • Value, Returns a value containing JSON serializable