Object built-in object

Object LevelDB

LevelDB database objects

Used to create and manage dictionary objects, creation method:

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

Inheritance

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, or null if it does not exist

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

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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 in the database between from and to

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

Call parameters:

  • from : Buffer , the smallest 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 , returns 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