deno-pg-format

Deno 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 Deno buffers, arrays, and objects which is explained below.

This project is a conversion to Deno from the original Node.js version made by Ryan Pedela.

Install

import { format } from 'https://deno.land/x/pg-format@v1.0.0/index.js';

Example

import { format } from 'https://deno.land/x/pg-format@v1.0.0/index.js';
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

format(fmt, …)

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.

import { format } from 'https://deno.land/x/pg-format@v1.0.0/index.js';
const sql = format('SELECT %1$L, %1$L, %L', 34, 'test');
console.log(sql); // SELECT '34', '34', 'test'

format.config(cfg)

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.

import { format } from 'https://deno.land/x/pg-format@v1.0.0/index.js';
format.config({
    pattern: {
        ident: 'V',
        literal: 'C',
        string: 't'
    }
});
format.config(); // reset to default

format.ident(input)

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

format.literal(input)

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

format.string(input)

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.

format.withArray(fmt, array)

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.

Deno Buffers

Deno.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.

import { format } from 'https://deno.land/x/pg-format@v1.0.0/index.js';

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

const 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

deno test