app.get('/rdp/host/:host?', function (req, res, next) {

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Limit Cyclomatic Complexity (complexity)

Cyclomatic complexity measures the number of linearly independent paths through a program's source code. This rule allows setting a cyclomatic complexity threshold.

function a(x) {
    if (true) {
        return x; // 1st path
    } else if (false) {
        return x+1; // 2nd path
    } else {
        return 4; // 3rd path
    }
}

Rule Details

This rule is aimed at reducing code complexity by capping the amount of cyclomatic complexity allowed in a program. As such, it will warn when the cyclomatic complexity crosses the configured threshold (default is 20).

Examples of incorrect code for a maximum of 2:

/*eslint complexity: ["error", 2]*/

function a(x) {
    if (true) {
        return x;
    } else if (false) {
        return x+1;
    } else {
        return 4; // 3rd path
    }
}

Examples of correct code for a maximum of 2:

/*eslint complexity: ["error", 2]*/

function a(x) {
    if (true) {
        return x;
    } else {
        return 4;
    }
}

Options

Optionally, you may specify a max object property:

"complexity": ["error", 2]

is equivalent to

"complexity": ["error", { "max": 2 }]

Deprecated: the object property maximum is deprecated. Please use the property max instead.

When Not To Use It

If you can't determine an appropriate complexity limit for your code, then it's best to disable this rule.

Further Reading

• About Complexity
• Complexity Analysis of JavaScript Code

Related Rules

• [max-depth](max-depth.md)
• [max-len](max-len.md)
• [max-nested-callbacks](max-nested-callbacks.md)
• [max-params](max-params.md)
• [max-statements](max-statements.md) Source: http://eslint.org/docs/rules/

  (socket.request.res) ? session(socket.request, socket.request.res, next) : next()

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Enforce Return After Callback (callback-return)

The callback pattern is at the heart of most I/O and event-driven programming in JavaScript.

function doSomething(err, callback) {
    if (err) {
        return callback(err);
    }
    callback();
}

To prevent calling the callback multiple times it is important to return anytime the callback is triggered outside of the main function body. Neglecting this technique often leads to issues where you do something more than once. For example, in the case of an HTTP request, you may try to send HTTP headers more than once leading Node.js to throw a Can't render headers after they are sent to the client. error.

Rule Details

This rule is aimed at ensuring that callbacks used outside of the main function block are always part-of or immediately preceding a return statement. This rule decides what is a callback based on the name of the function being called.

Options

The rule takes a single option - an array of possible callback names - which may include object methods. The default callback names are callback, cb, next.

Default callback names

Examples of incorrect code for this rule with the default ["callback", "cb", "next"] option:

/*eslint callback-return: "error"*/

function foo(err, callback) {
    if (err) {
        callback(err);
    }
    callback();
}

Examples of correct code for this rule with the default ["callback", "cb", "next"] option:

/*eslint callback-return: "error"*/

function foo(err, callback) {
    if (err) {
        return callback(err);
    }
    callback();
}

Supplied callback names

Examples of incorrect code for this rule with the option ["done", "send.error", "send.success"]:

/*eslint callback-return: ["error", ["done", "send.error", "send.success"]]*/

function foo(err, done) {
    if (err) {
        done(err);
    }
    done();
}

function bar(err, send) {
    if (err) {
        send.error(err);
    }
    send.success();
}

Examples of correct code for this rule with the option ["done", "send.error", "send.success"]:

/*eslint callback-return: ["error", ["done", "send.error", "send.success"]]*/

function foo(err, done) {
    if (err) {
        return done(err);
    }
    done();
}

function bar(err, send) {
    if (err) {
        return send.error(err);
    }
    send.success();
}

Known Limitations

Because it is difficult to understand the meaning of a program through static analysis, this rule has limitations:

• false negatives when this rule reports correct code, but the program calls the callback more than one time (which is incorrect behavior)
• false positives when this rule reports incorrect code, but the program calls the callback only one time (which is correct behavior)

Passing the callback by reference

The static analysis of this rule does not detect that the program calls the callback if it is an argument of a function (for example, setTimeout).

Example of a false negative when this rule reports correct code:

/*eslint callback-return: "error"*/

function foo(err, callback) {
    if (err) {
        setTimeout(callback, 0); // this is bad, but WILL NOT warn
    }
    callback();
}

Triggering the callback within a nested function

The static analysis of this rule does not detect that the program calls the callback from within a nested function or an immediately-invoked function expression (IIFE).

Example of a false negative when this rule reports correct code:

/*eslint callback-return: "error"*/

function foo(err, callback) {
    if (err) {
        process.nextTick(function() {
            return callback(); // this is bad, but WILL NOT warn
        });
    }
    callback();
}

If/else statements

The static analysis of this rule does not detect that the program calls the callback only one time in each branch of an if statement.

Example of a false positive when this rule reports incorrect code:

/*eslint callback-return: "error"*/

function foo(err, callback) {
    if (err) {
        callback(err); // this is fine, but WILL warn
    } else {
        callback();    // this is fine, but WILL warn
    }
}

When Not To Use It

There are some cases where you might want to call a callback function more than once. In those cases this rule may lead to incorrect behavior. In those cases you may want to reserve a special name for those callbacks and not include that in the list of callbacks that trigger warnings.

Further Reading

• The Art Of Node: Callbacks
• Nodejitsu: What are the error conventions?

Related Rules

• [handle-callback-err](handle-callback-err.md) Source: http://eslint.org/docs/rules/

  (socket.request.res) ? session(socket.request, socket.request.res, next) : next()

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Disallow Unused Expressions (no-unused-expressions)

An unused expression which has no effect on the state of the program indicates a logic error.

For example, n + 1; is not a syntax error, but it might be a typing mistake where a programmer meant an assignment statement n += 1; instead.

Rule Details

This rule aims to eliminate unused expressions which have no effect on the state of the program.

This rule does not apply to function calls or constructor calls with the new operator, because they could have side effects on the state of the program.

var i = 0;
function increment() { i += 1; }
increment(); // return value is unused, but i changed as a side effect

var nThings = 0;
function Thing() { nThings += 1; }
new Thing(); // constructed object is unused, but nThings changed as a side effect

This rule does not apply to directives (which are in the form of literal string expressions such as "use strict"; at the beginning of a script, module, or function).

Sequence expressions (those using a comma, such as a = 1, b = 2) are always considered unused unless their return value is assigned or used in a condition evaluation, or a function call is made with the sequence expression value.

Options

This rule, in its default state, does not require any arguments. If you would like to enable one or more of the following you may pass an object with the options set as follows:

• allowShortCircuit set to true will allow you to use short circuit evaluations in your expressions (Default: false).
• allowTernary set to true will enable you to use ternary operators in your expressions similarly to short circuit evaluations (Default: false).
• allowTaggedTemplates set to true will enable you to use tagged template literals in your expressions (Default: false).

These options allow unused expressions only if all of the code paths either directly change the state (for example, assignment statement) or could have side effects (for example, function call).

Examples of incorrect code for the default { "allowShortCircuit": false, "allowTernary": false } options:

/*eslint no-unused-expressions: "error"*/

0

if(0) 0

{0}

f(0), {}

a && b()

a, b()

c = a, b;

a() && function namedFunctionInExpressionContext () {f();}

(function anIncompleteIIFE () {});

injectGlobal`body{ color: red; }`

Note that one or more string expression statements (with or without semi-colons) will only be considered as unused if they are not in the beginning of a script, module, or function (alone and uninterrupted by other statements). Otherwise, they will be treated as part of a "directive prologue", a section potentially usable by JavaScript engines. This includes "strict mode" directives.

"use strict";
"use asm"
"use stricter";
"use babel"
"any other strings like this in the prologue";

Examples of correct code for the default { "allowShortCircuit": false, "allowTernary": false } options:

/*eslint no-unused-expressions: "error"*/

{} // In this context, this is a block statement, not an object literal

{myLabel: someVar} // In this context, this is a block statement with a label and expression, not an object literal

function namedFunctionDeclaration () {}

(function aGenuineIIFE () {}());

f()

a = 0

new C

delete a.b

void a

allowShortCircuit

Examples of incorrect code for the { "allowShortCircuit": true } option:

/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/

a || b

Examples of correct code for the { "allowShortCircuit": true } option:

/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true }]*/

a && b()
a() || (b = c)

allowTernary

Examples of incorrect code for the { "allowTernary": true } option:

/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/

a ? b : 0
a ? b : c()

Examples of correct code for the { "allowTernary": true } option:

/*eslint no-unused-expressions: ["error", { "allowTernary": true }]*/

a ? b() : c()
a ? (b = c) : d()

allowShortCircuit and allowTernary

Examples of correct code for the { "allowShortCircuit": true, "allowTernary": true } options:

/*eslint no-unused-expressions: ["error", { "allowShortCircuit": true, "allowTernary": true }]*/

a ? b() || (c = d) : e()

allowTaggedTemplates

Examples of incorrect code for the { "allowTaggedTemplates": true } option:

/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/

`some untagged template string`;

Examples of correct code for the { "allowTaggedTemplates": true } option:

/*eslint no-unused-expressions: ["error", { "allowTaggedTemplates": true }]*/

tag`some tagged template string`;

Source: http://eslint.org/docs/rules/

    readyTimeout: (validator.isInt(req.query.readyTimeout + '', {min: 1, max: 300000}) &&
      req.query.readyTimeout) || config.rdp.readyTimeout

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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 61.

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

    port: (validator.isInt(req.query.port + '', {min: 1, max: 65535}) &&
      req.query.port) || config.rdp.port,

Close

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 61.

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

  if (req.session.rdp.header.name) validator.escape(req.session.rdp.header.name)

Close

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 47.

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

  if (req.session.rdp.header.background) validator.escape(req.session.rdp.header.background)

Close

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 47.

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