disallow multiple empty lines (no-multiple-empty-lines)

Some developers prefer to have multiple blank lines removed, while others feel that it helps improve readability. Whitespace is useful for separating logical sections of code, but excess whitespace takes up more of the screen.

Rule Details

This rule aims to reduce the scrolling required when reading through your code. It will warn when the maximum amount of empty lines has been exceeded.

Options

This rule has an object option:

• "max" (default: 2) enforces a maximum number of consecutive empty lines.
• "maxEOF" enforces a maximum number of consecutive empty lines at the end of files.
• "maxBOF" enforces a maximum number of consecutive empty lines at the beginning of files.

max

Examples of incorrect code for this rule with the default { "max": 2 } option:

/*eslint no-multiple-empty-lines: "error"*/

var foo = 5;



var bar = 3;

Examples of correct code for this rule with the default { "max": 2 } option:

/*eslint no-multiple-empty-lines: "error"*/

var foo = 5;


var bar = 3;

maxEOF

Examples of incorrect code for this rule with the { max: 2, maxEOF: 1 } options:

/*eslint no-multiple-empty-lines: ["error", { "max": 2, "maxEOF": 1 }]*/

var foo = 5;


var bar = 3;

Examples of correct code for this rule with the { max: 2, maxEOF: 1 } options:

/*eslint no-multiple-empty-lines: ["error", { "max": 2, "maxEOF": 1 }]*/

var foo = 5;


var bar = 3;

maxBOF

Examples of incorrect code for this rule with the { max: 2, maxBOF: 1 } options:

/*eslint no-multiple-empty-lines: ["error", { "max": 2, "maxBOF": 1 }]*/


var foo = 5;


var bar = 3;

Examples of correct code for this rule with the { max: 2, maxBOF: 1 } options:

/*eslint no-multiple-empty-lines: ["error", { "max": 2, "maxBOF": 1}]*/

var foo = 5;


var bar = 3;

When Not To Use It

If you do not care about extra blank lines, turn this off. Source: http://eslint.org/docs/rules/

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 53.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 51.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76