Require Dot Notation (dot-notation)

In JavaScript, one can access properties using the dot notation ( or square-bracket notation (foo["bar"]). However, the dot notation is often preferred because it is easier to read, less verbose, and works better with aggressive JavaScript minimizers.


Rule Details

This rule is aimed at maintaining code consistency and improving code readability by encouraging use of the dot notation style whenever possible. As such, it will warn when it encounters an unnecessary use of square-bracket notation.

The following patterns are considered warnings:

var x = foo["bar"];

The following patterns are not considered warnings:

var x =;

var x = foo[bar];    // Property name is a variable, square-bracket notation required


This rule accepts a single options argument with the following defaults:

    "rules": {
        "dot-notation": [2, {"allowKeywords": true, "allowPattern": ""}]


Set the allowKeywords option to false (default is true) to follow ECMAScript version 3 compatible style, avoiding dot notation for reserved word properties.

  "dot-notation": [2, {"allowKeywords": false}],
var foo = { "class": "CS 101" }
var x = foo["class"]; // Property name is a reserved word, square-bracket notation required


Set the allowPattern option to a regular expression string to allow bracket notation for property names that match a pattern (by default, no pattern is tested).

For example, when preparing data to be sent to an external API, it is often required to use property names that include underscores. If the camelcase rule is in effect, these snake case properties would not be allowed. By providing an allowPattern to the dot-notation rule, these snake case properties can be accessed with bracket notation.

Example configuration:

    "rules": {
        "camelcase": 2
        "dot-notation": [2, {"allowPattern": "^[a-z]+(_[a-z]+)+$"}]

Example code patterns:

var data = {};
data.foo_bar = 42; // warning from camelcase

var data = {};
data["fooBar"] = 42; // warning from dot-notation

var data = {};
data["foo_bar"] = 42; // no warning


This rule was introduced in ESLint 0.0.7.