Update

_drafts/postgresql-json.md

@@ -8,8 +8,34 @@ SELECT * FROM users WHERE data->>'name' = 'John'
 SELECT data->>'name' AS name FROM users
 ```
 
-| Postgres | JavaScript pseudocode |
+| Operator | Example          | Description                        | Returns |
-| ---- | ---- |
+| ----     | ----             | ----                               | ----    |
-| WHERE `data->>'name'` = 'John' | `data.name` |
+| `->`     | `data->2`        | Get array element `2`              | JSON    |
-| WHERE `data ? 'name'`          | `data.hasOwnProperty('name')` |
+| `->`     | `data->'name'`   | Get object key `name`              | JSON    |
-| `jsonb_array_elements_text(data->'tags')`          | `data.map(d => d.tags).flatten.uniq` |
+| `#>`     | `data#>'{a,b}'`  | Get keypath `a,b` (eg, `data.a.b`) | JSON    |
+| ----     | ----             | ----                               | ----    |
+| `->>`    | `data->>2`       | Get array element `2`              | text    |
+| `->>`    | `data->>'name'`  | Get object key `name`              | text    |
+| `#>`     | `data#>>'{a,b}'` | Get keypath `a,b` (eg, `data.a.b`) | text    |
+
+`>` returns JSON, `>>` returns text.
+
+### Boolean operators
+
+| Operator | Example                                      | Description                     |
+| ----     | ----                                         | ----                            |
+| `?`      | `data ? 'name'`                              | Does `data` have key `name`?    |
+| `?|`     | `data ?| array['a','b']`                     | Does `data` have `a` or `b`?    |
+| `?&`     | `data ?& array['a','b']`                     | Does `data` have `a` and `b`?   |
+| `@>`     | `'{"a":1,"b":2}'::jsonb @> '{"b":2}'::jsonb` | Does `left` include `right`?    |
+| `<@`     | `'{"a":1}'::jsonb <@ '{"a":1,"b":2}'::jsonb` | Does `right` include `left`?    |
+
+When `?`/`?|`/`?&` works on objects, it checks keys; when it works on arrays, it checks for elements.
+
+- `'{"a":1}'::jsonb ? 'a'`
+- `'["a"]'::jsonb ? 'a'`
+
+## References
+
+- <https://www.postgresql.org/docs/9.4/static/functions-json.html>
+- <https://www.postgresql.org/docs/9.4/static/datatype-json.html>

yarn.md

@@ -6,7 +6,7 @@ category: JavaScript libraries
 | npm | yarn |
 | --- | ---- |
 | `npm install` | `yarn` |
-| `npm install gulp` | `yarn add gulp` |
+| `npm install gulp --save` | `yarn add gulp` |
 | `npm install gulp --save-dev --save-exact` | `yarn add gulp --dev --exact` |
 | `npm install -g gulp` | `yarn global add gulp` |
 | `./node_modules/.bin/gulp` | `yarn run gulp` |