map.keys()
, map.values()
, map.entries()
.Map
Set
Array
[key, value]
pairs.Map | Object | |
---|---|---|
Call syntax | map.keys() | Object.keys(obj) , but not obj.keys() |
Returns | iterable | “real” Array |
Object.keys(obj)
, and not obj.keys()
.data
that implements its own data.values()
method. And we still can call Object.values(data)
on it.Object.*
methods return “real” array objects, not just an iterable. That’s mainly for historical reasons.Object.keys(user) = ['name', 'age']
Object.values(user) = ['John', 30]
Object.entries(user) = [ ['name','John'], ['age',30] ]
Object.values
to loop over property values:for..in
loop, these methods ignore properties that use Symbol(...)
as keys.map
, filter
and others.Object.entries
followed Object.fromEntries
:Object.entries(obj)
to get an array of key/value pairs from obj
.map
.Object.fromEntries(array)
on the resulting array to turn it back into an object.Operator | Right Operand Type | Description | Example | Example Result |
---|---|---|---|---|
-> | int | Get JSON array element (indexed from zero, negative integers count from the end) | '[{'a':'foo'},{'b':'bar'},{'c':'baz'}]'::json->2 | {'c':'baz'} |
-> | text | Get JSON object field by key | '{'a': {'b':'foo'}}'::json->'a' | {'b':'foo'} |
->> | int | Get JSON array element as text | '[1,2,3]'::json->>2 | 3 |
->> | text | Get JSON object field as text | '{'a':1,'b':2}'::json->>'b' | 2 |
#> | text[] | Get JSON object at specified path | '{'a': {'b':{'c': 'foo'}}}'::json#>'{a,b}' | {'c': 'foo'} |
#>> | text[] | Get JSON object at specified path as text | '{'a':[1,2,3],'b':[4,5,6]}'::json#>>'{a,2}' | 3 |
Operator | Right Operand Type | Description | Example |
---|---|---|---|
@> | jsonb | Does the left JSON value contain the right JSON path/value entries at the top level? | '{'a':1, 'b':2}'::jsonb @> '{'b':2}'::jsonb |
<@ | jsonb | Are the left JSON path/value entries contained at the top level within the right JSON value? | '{'b':2}'::jsonb <@ '{'a':1, 'b':2}'::jsonb |
? | text | Does the string exist as a top-level key within the JSON value? | '{'a':1, 'b':2}'::jsonb ? 'b' |
?| | text[] | Do any of these array strings exist as top-level keys? | '{'a':1, 'b':2, 'c':3}'::jsonb ?| array['b', 'c'] |
?& | text[] | Do all of these array strings exist as top-level keys? | '['a', 'b']'::jsonb ?& array['a', 'b'] |
|| | jsonb | Concatenate two jsonb values into a new jsonb value | '['a', 'b']'::jsonb || '['c', 'd']'::jsonb |
- | text | Delete key/value pair or string element from left operand. Key/value pairs are matched based on their key value. | '{'a': 'b'}'::jsonb - 'a' |
- | integer | Delete the array element with specified index (Negative integers count from the end). Throws an error if top level container is not an array. | '['a', 'b']'::jsonb - 1 |
#- | text[] | Delete the field or element with specified path (for JSON arrays, negative integers count from the end) | '['a', {'b':1}]'::jsonb #- '{1,b}' |
Function | Description | Example | Example Result |
---|---|---|---|
to_json(anyelement) to_jsonb(anyelement) | Returns the value as json or jsonb. Arrays and composites are converted (recursively) to arrays and objects; otherwise, if there is a cast from the type to json, the cast function will be used to perform the conversion; otherwise, a scalar value is produced. For any scalar type other than a number, a Boolean, or a null value, the text representation will be used, in such a fashion that it is a valid json or jsonb value. | to_json('Fred said 'Hi.'::text) | 'Fred said 'Hi.' |
array_to_json(anyarray [, pretty_bool]) | Returns the array as a JSON array. A PostgreSQL multidimensional array becomes a JSON array of arrays. Line feeds will be added between dimension-1 elements if pretty_bool is true. | array_to_json('{{1,5},{99,100}}'::int[]) | [[1,5],[99,100]] |
row_to_json(record [, pretty_bool]) | Returns the row as a JSON object. Line feeds will be added between level-1 elements if pretty_bool is true. | row_to_json(row(1,'foo')) | {'f1':1,'f2':'foo'} |
json_build_array(VARIADIC 'any') jsonb_build_array(VARIADIC 'any') | Builds a possibly-heterogeneously-typed JSON array out of a variadic argument list. | json_build_array(1,2,'3',4,5) | [1, 2, '3', 4, 5] |
json_build_object(VARIADIC 'any') jsonb_build_object(VARIADIC 'any') | Builds a JSON object out of a variadic argument list. By convention, the argument list consists of alternating keys and values. | json_build_object('foo',1,'bar',2) | {'foo': 1, 'bar': 2} |
json_object(text[]) jsonb_object(text[]) | Builds a JSON object out of a text array. The array must have either exactly one dimension with an even number of members, in which case they are taken as alternating key/value pairs, or two dimensions such that each inner array has exactly two elements, which are taken as a key/value pair. | json_object('{a, 1, b, 'def', c, 3.5}') json_object('{{a, 1},{b, 'def'},{c, 3.5}}') | {'a': '1', 'b': 'def', 'c': '3.5'} |
json_object(keys text[], values text[]) jsonb_object(keys text[], values text[]) | This form of json_object takes keys and values pairwise from two separate arrays. In all other respects it is identical to the one-argument form. | json_object('{a, b}', '{1,2}') | {'a': '1', 'b': '2'} |
array_to_json
and row_to_json
have the same behavior as to_json
except for offering a pretty-printing option. The behavior described for to_json
likewise applies to each individual value converted by the other JSON creation functions.Function | Return Type | Description | Example | Example Result |
---|---|---|---|---|
json_array_length(json) jsonb_array_length(jsonb) | int | Returns the number of elements in the outermost JSON array. | json_array_length('[1,2,3,{'f1':1,'f2':[5,6]},4]') | 5 |
json_each(json) jsonb_each(jsonb) | setof key text, value json setof key text, value jsonb | Expands the outermost JSON object into a set of key/value pairs. | select * from json_each('{'a':'foo', 'b':'bar'}') | |
json_each_text(json) jsonb_each_text(jsonb) | setof key text, value text | Expands the outermost JSON object into a set of key/value pairs. The returned values will be of type text. | select * from json_each_text('{'a':'foo', 'b':'bar'}') | |
json_extract_path(from_json json, VARIADIC path_elems text[]) jsonb_extract_path(from_json jsonb, VARIADIC path_elems text[]) | json jsonb | Returns JSON value pointed to by path_elems (equivalent to #> operator). | json_extract_path('{'f2':{'f3':1},'f4':{'f5':99,'f6':'foo'}}','f4') | {'f5':99,'f6':'foo'} |
json_extract_path_text(from_json json, VARIADIC path_elems text[]) jsonb_extract_path_text(from_json jsonb, VARIADIC path_elems text[]) | text | Returns JSON value pointed to by path_elems as text (equivalent to #>> operator). | json_extract_path_text('{'f2':{'f3':1},'f4':{'f5':99,'f6':'foo'}}','f4', 'f6') | foo |
json_object_keys(json) jsonb_object_keys(jsonb) | setof text | Returns set of keys in the outermost JSON object. | json_object_keys('{'f1':'abc','f2':{'f3':'a', 'f4':'b'}}') | |
json_populate_record(base anyelement, from_json json) jsonb_populate_record(base anyelement, from_json jsonb) | anyelement | Expands the object in from_json to a row whose columns match the record type defined by base (see note below). | select * from json_populate_record(null::myrowtype, '{'a':1,'b':2}') | |
json_populate_recordset(base anyelement, from_json json) jsonb_populate_recordset(base anyelement, from_json jsonb) | setof anyelement | Expands the outermost array of objects in from_json to a set of rows whose columns match the record type defined by base (see note below). | select * from json_populate_recordset(null::myrowtype, '[{'a':1,'b':2},{'a':3,'b':4}]') | |
json_array_elements(json) jsonb_array_elements(jsonb) | setof json setof jsonb | Expands a JSON array to a set of JSON values. | select * from json_array_elements('[1,true, [2,false]]') | |
json_array_elements_text(json) jsonb_array_elements_text(jsonb) | setof text | Expands a JSON array to a set of text values. | select * from json_array_elements_text('['foo', 'bar']') | |
json_typeof(json) jsonb_typeof(jsonb) | text | Returns the type of the outermost JSON value as a text string. Possible types are object, array, string, number, boolean, and null. | json_typeof('-123.4') | number |
json_to_record(json) jsonb_to_record(jsonb) | record | Builds an arbitrary record from a JSON object (see note below). As with all functions returning record, the caller must explicitly define the structure of the record with an AS clause. | select * from json_to_record('{'a':1,'b':[1,2,3],'c':'bar'}') as x(a int, b text, d text) | |
json_to_recordset(json) jsonb_to_recordset(jsonb) | setof record | Builds an arbitrary set of records from a JSON array of objects (see note below). As with all functions returning record, the caller must explicitly define the structure of the record with an AS clause. | select * from json_to_recordset('[{'a':1,'b':'foo'},{'a':'2','c':'bar'}]') as x(a int, b text); | |
json_strip_nulls(from_json json) jsonb_strip_nulls(from_json jsonb) | json jsonb | Returns from_json with all object fields that have null values omitted. Other null values are untouched. | json_strip_nulls('[{'f1':1,'f2':null},2,null,3]') | [{'f1':1},2,null,3] |
jsonb_set(target jsonb, path text[], new_value jsonb [, create_missing boolean]) | jsonb | Returns target with the section designated by path replaced by new_value, or with new_value added if create_missing is true (default is true) and the item designated by path does not exist. As with the path oriented operators, negative integers that appear in path count from the end of JSON arrays. | jsonb_set('[{'f1':1,'f2':null},2,null,3]', '{0,f1}','[2,3,4]', false) jsonb_set('[{'f1':1,'f2':null},2]', '{0,f3}','[2,3,4]') | [{'f1':[2,3,4],'f2':null},2,null,3] [{'f1': 1, 'f2': null, 'f3': [2, 3, 4]}, 2] |
jsonb_pretty(from_json jsonb) | text | Returns from_json as indented JSON text. | jsonb_pretty('[{'f1':1,'f2':null},2,null,3]') |
json_populate_record
, json_populate_recordset
, json_to_record
and json_to_recordset
use constants, the typical use would be to reference a table in the FROM clause and use one of its json or jsonb columns as an argument to the function. Extracted key values can then be referenced in other parts of the query, like WHERE clauses and target lists. Extracting multiple values in this way can improve performance over extracting them separately with per-key operators.json_agg
which aggregates record values as JSON, and the aggregate function json_object_agg
which aggregates pairs of values into a JSON object, and their jsonb equivalents, jsonb_agg
and jsonb_object_agg
.