Require Dot Notation (dot-notation)

The --fix option on the command line automatically fixes problems reported by this rule.

In JavaScript, one can access properties using the dot notation (foo.bar) 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.

foo["bar"];

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.

Examples of incorrect code for this rule:

/*eslint dot-notation: "error"*/

var x = foo["bar"];

Examples of correct code for this rule:

/*eslint dot-notation: "error"*/

var x = foo.bar;

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

Options

This rule accepts a single options argument:

allowKeywords

Examples of correct code for the { "allowKeywords": false } option:

/*eslint dot-notation: ["error", { "allowKeywords": false }]*/

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

allowPattern

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.

Examples of correct code for the sample { "allowPattern": "^[a-z]+(_[a-z]+)+$" } option:

/*eslint camelcase: "error"*/
/*eslint dot-notation: ["error", { "allowPattern": "^[a-z]+(_[a-z]+)+$" }]*/

var data = {};
data.foo_bar = 42;

var data = {};
data["fooBar"] = 42;

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

Version

This rule was introduced in ESLint 0.0.7.

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