node-pg-format

node-pg-format
==============

Node.js implementation of PostgreSQL format() to safely create dynamic SQL queries. SQL identifiers and literals are escaped to help prevent SQL injection. The behavior is equivalent to PostgreSQL format(). This module also supports Node buffers, arrays, and objects which is explained below.

Install

npm install node-pg-format

Example

``js
import { format } from 'node-pg-format';
const sql = format('SELECT * FROM %I WHERE my_col = %L %s', 'my_table', 34, 'LIMIT 10');
console.log(sql); // SELECT * FROM my_table WHERE my_col = 34 LIMIT 10
`

API

$3

Returns a formatted string based on `fmt` which has a style similar to the C function `sprintf()`.
* `%%` outputs a literal `%` character.
* `%I` outputs an escaped SQL identifier.
* `%L` outputs an escaped SQL literal.
* `%s` outputs a simple string.

#### Argument position
You can define where an argument is positioned using `n$` where `n` is the argument index starting at 1.
`js
import { format } from 'node-pg-format';
const sql = format('SELECT %1$L, %1$L, %L', 34, 'test');
console.log(sql); // SELECT 34, 34, 'test'
`

$3


Changes the global configuration. You can change which letters are used to denote identifiers, literals, and strings in the formatted string. This is useful when the formatted string contains a PL/pgSQL function which calls PostgreSQL format() itself.
`js
import { format } from 'node-pg-format';
format.config({
pattern: {
ident: 'V',
literal: 'C',
string: 't'
}
});
format.config(); // reset to default
`

$3

Returns the input as an escaped SQL identifier string. `undefined`, `null`, and objects will throw an error.

$3

Returns the input as an escaped SQL literal string. `undefined` and `null` will return `'NULL'`;

$3

Returns the input as a simple string. `undefined` and `null` will return an empty string. If an array element is `undefined` or `null`, it will be removed from the output string.

$3

Same as `format(fmt, ...)` except parameters are provided in an array rather than as function arguments. This is useful when dynamically creating a SQL query and the number of parameters is unknown or variable.

Node Buffers

Node buffers can be used for literals (`%L`) and strings (`%s`), and will be converted to PostgreSQL bytea hex format.

Arrays and Objects

For arrays, each element is escaped when appropriate and concatenated to a comma-delimited string. Nested arrays are turned into grouped lists (for bulk inserts), e.g. [['a', 'b'], ['c', 'd']] turns into ('a', 'b'), ('c', 'd'). Nested array expansion can be used for literals (`%L`) and strings (`%s`), but not identifiers (`%I`).
For objects, `JSON.stringify()` is called and the resulting string is escaped if appropriate. Objects can be used for literals (`%L`) and strings (`%s`), but not identifiers (`%I`). See the example below.

`js
import { format } from 'node-pg-format';

const myArray = [ 1, 2, 3 ];
const myObject = { a: 1, b: 2 };
const myNestedArray = [['a', 1], ['b', 2]];

let sql = format('SELECT * FROM t WHERE c1 IN (%L) AND c2 = %L', myArray, myObject);
console.log(sql); // SELECT * FROM t WHERE c1 IN (1,2,3) AND c2 = '{"a":1,"b":2}'

sql = format('INSERT INTO t (name, age) VALUES %L', myNestedArray);
console.log(sql); // INSERT INTO t (name, age) VALUES ('a', 1), ('b', 2)
`

Testing

`
npm install
npm run build
npm test
``