Limit Maximum Length of Line (max-len)

Very long lines of code in any language can be difficult to read. In order to aid in readability and maintainability many coders have developed a convention to limit lines of code to X number of characters (traditionally 80 characters).

// max-len: [1, 80, 4]; // maximum length of 80 characters
var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" }, "difficult": "to read" }; // too long

Rule Details

This rule is aimed at increasing code readability and maintainability by enforcing a line length convention. As such it will warn on lines that exceed the configured maximum.

Note: This rule calculates the length of a line via code points, not characters. That means if you use a double-byte character in your code, it will count as 2 code points instead of 1, and 2 will be used to calculate line length. This is a technical limitation of JavaScript that is made easier with ES2015, and we will look to update this when ES2015 is available in Node.js.

The following patterns are considered problems:

/*eslint max-len: [2, 80, 4]*/ // maximum length of 80 characters

var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" }, "difficult": "to read" }; /*error Line 3 exceeds the maximum line length of 80.*/

The following patterns are not considered problems:

/*eslint max-len: [2, 80, 4]*/ // maximum length of 80 characters

var foo = {
    "bar": "This is a bar.",
    "baz": {
        "qux": "This is a qux"
    },
    "difficult": "to read"
};

Options

The max-len rule supports the following options:

code: The total number of characters allowed on each line of code. This character count includes indentation. Defaults to 80.

comments: The total number of characters allowed on a line of comments (e.g. no code on the line). If not specified, code is used for comment lines.

tabWidth: The character count to use whenever a tab character is encountered. Defaults to 4.

ignoreComments: Ignores all trailing comments and comments on their own line. For example, function foo(/*string*/ bar) { /* ... */ } isn’t collapsed.

ignoreTrailingComments: Only ignores comments that are trailing source.

commentLength: Specifies an alternate max length that applies only to full length comments.

ignoreUrls: Ignores lines that contain a URL.

ignorePattern: Ignores lines matching a regular express, such as ^\\s*var\\s.+=\\s*require\\s*\\(. Be aware that regular expressions can only match a single line and need to be doubly escaped when written in YAML or JSON.

Optionally, you may specify code and tabWidth as integers before the options object:

"max-len": [2, 80, 4, {"ignoreUrls": true}]

is equivalent to

"max-len": [2, {"code": 80, "tabWidth": 4, "ignoreUrls": true}]

Version

This rule was introduced in ESLint 0.0.9.

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