huridocs/uwazi

title: max-params ruletype: suggestion relatedrules: - complexity - max-depth - max-len - max-lines - max-lines-per-function - max-nested-callbacks

- max-statements

Functions that take numerous parameters can be difficult to read and write because it requires the memorization of what each parameter is, its type, and the order they should appear in. As a result, many coders adhere to a convention that caps the number of parameters a function can take.

function foo (bar, baz, qux, qxx) { // four parameters, may be too many
    doSomething();
}

Rule Details

This rule enforces a maximum number of parameters allowed in function definitions.

Options

This rule has a number or object option:

• "max" (default 3) enforces a maximum number of parameters in function definitions

Deprecated: The object property maximum is deprecated; please use the object property max instead.

max

Examples of incorrect code for this rule with the default { "max": 3 } option:

:::incorrect

/*eslint max-params: ["error", 3]*/
/*eslint-env es6*/
 
function foo (bar, baz, qux, qxx) {
    doSomething();
}
 
let foo = (bar, baz, qux, qxx) => {
    doSomething();
};

:::

Examples of correct code for this rule with the default { "max": 3 } option:

:::correct

/*eslint max-params: ["error", 3]*/
/*eslint-env es6*/
 
function foo (bar, baz, qux) {
    doSomething();
}
 
let foo = (bar, baz, qux) => {
    doSomething();
};

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

title: max-statements ruletype: suggestion relatedrules: - complexity - max-depth - max-len - max-lines - max-lines-per-function - max-nested-callbacks

- max-params

The max-statements rule allows you to specify the maximum number of statements allowed in a function.

function foo() {
  var bar = 1; // one statement
  var baz = 2; // two statements
  var qux = 3; // three statements
}

Rule Details

This rule enforces a maximum number of statements allowed in function blocks.

Options

This rule has a number or object option:

• "max" (default 10) enforces a maximum number of statements allows in function blocks

Deprecated: The object property maximum is deprecated; please use the object property max instead.

This rule has an object option:

• "ignoreTopLevelFunctions": true ignores top-level functions

max

Examples of incorrect code for this rule with the default { "max": 10 } option:

::: incorrect

/*eslint max-statements: ["error", 10]*/
/*eslint-env es6*/
 
function foo() {
  var foo1 = 1;
  var foo2 = 2;
  var foo3 = 3;
  var foo4 = 4;
  var foo5 = 5;
  var foo6 = 6;
  var foo7 = 7;
  var foo8 = 8;
  var foo9 = 9;
  var foo10 = 10;
 
  var foo11 = 11; // Too many.
}
 
let foo = () => {
  var foo1 = 1;
  var foo2 = 2;
  var foo3 = 3;
  var foo4 = 4;
  var foo5 = 5;
  var foo6 = 6;
  var foo7 = 7;
  var foo8 = 8;
  var foo9 = 9;
  var foo10 = 10;
 
  var foo11 = 11; // Too many.
};

:::

Examples of correct code for this rule with the default { "max": 10 } option:

::: correct

/*eslint max-statements: ["error", 10]*/
/*eslint-env es6*/
 
function foo() {
  var foo1 = 1;
  var foo2 = 2;
  var foo3 = 3;
  var foo4 = 4;
  var foo5 = 5;
  var foo6 = 6;
  var foo7 = 7;
  var foo8 = 8;
  var foo9 = 9;
  var foo10 = 10;
  return function () {
 
    // The number of statements in the inner function does not count toward the
    // statement maximum.
 
    return 42;
  };
}
 
let foo = () => {
  var foo1 = 1;
  var foo2 = 2;
  var foo3 = 3;
  var foo4 = 4;
  var foo5 = 5;
  var foo6 = 6;
  var foo7 = 7;
  var foo8 = 8;
  var foo9 = 9;
  var foo10 = 10;
  return function () {
 
    // The number of statements in the inner function does not count toward the
    // statement maximum.
 
    return 42;
  };
}

:::

Note that this rule does not apply to class static blocks, and that statements in class static blocks do not count as statements in the enclosing function.

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

::: correct

/*eslint max-statements: ["error", 2]*/
 
function foo() {
    let one;
    let two = class {
        static {
            let three;
            let four;
            let five;
            if (six) {
                let seven;
                let eight;
                let nine;
            }
        }
    };
}

:::

ignoreTopLevelFunctions

Examples of additional correct code for this rule with the { "max": 10 }, { "ignoreTopLevelFunctions": true } options:

::: correct

/*eslint max-statements: ["error", 10, { "ignoreTopLevelFunctions": true }]*/
 
function foo() {
  var foo1 = 1;
  var foo2 = 2;
  var foo3 = 3;
  var foo4 = 4;
  var foo5 = 5;
  var foo6 = 6;
  var foo7 = 7;
  var foo8 = 8;
  var foo9 = 9;
  var foo10 = 10;
  var foo11 = 11;
}

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

title: consistent-return

rule_type: suggestion

Unlike statically-typed languages which enforce that a function returns a specified type of value, JavaScript allows different code paths in a function to return different types of values.

A confusing aspect of JavaScript is that a function returns undefined if any of the following are true:

• it does not execute a return statement before it exits
• it executes return which does not specify a value explicitly
• it executes return undefined
• it executes return void followed by an expression (for example, a function call)
• it executes return followed by any other expression which evaluates to undefined

If any code paths in a function return a value explicitly but some code path do not return a value explicitly, it might be a typing mistake, especially in a large function. In the following example:

• a code path through the function returns a Boolean value true
• another code path does not return a value explicitly, therefore returns undefined implicitly

function doSomething(condition) {
    if (condition) {
        return true;
    } else {
        return;
    }
}

Rule Details

This rule requires return statements to either always or never specify values. This rule ignores function definitions where the name begins with an uppercase letter, because constructors (when invoked with the new operator) return the instantiated object implicitly if they do not return another object explicitly.

Examples of incorrect code for this rule:

::: incorrect

/*eslint consistent-return: "error"*/
 
function doSomething(condition) {
    if (condition) {
        return true;
    } else {
        return;
    }
}
 
function doSomething(condition) {
    if (condition) {
        return true;
    }
}

:::

Examples of correct code for this rule:

::: correct

/*eslint consistent-return: "error"*/
 
function doSomething(condition) {
    if (condition) {
        return true;
    } else {
        return false;
    }
}
 
function Foo() {
    if (!(this instanceof Foo)) {
        return new Foo();
    }
 
    this.a = 0;
}

:::

Options

This rule has an object option:

• "treatUndefinedAsUnspecified": false (default) always either specify values or return undefined implicitly only.
• "treatUndefinedAsUnspecified": true always either specify values or return undefined explicitly or implicitly.

treatUndefinedAsUnspecified

Examples of incorrect code for this rule with the default { "treatUndefinedAsUnspecified": false } option:

::: incorrect

/*eslint consistent-return: ["error", { "treatUndefinedAsUnspecified": false }]*/
 
function foo(callback) {
    if (callback) {
        return void callback();
    }
    // no return statement
}
 
function bar(condition) {
    if (condition) {
        return undefined;
    }
    // no return statement
}

:::

Examples of incorrect code for this rule with the { "treatUndefinedAsUnspecified": true } option:

::: incorrect

/*eslint consistent-return: ["error", { "treatUndefinedAsUnspecified": true }]*/
 
function foo(callback) {
    if (callback) {
        return void callback();
    }
    return true;
}
 
function bar(condition) {
    if (condition) {
        return undefined;
    }
    return true;
}

:::

Examples of correct code for this rule with the { "treatUndefinedAsUnspecified": true } option:

::: correct

/*eslint consistent-return: ["error", { "treatUndefinedAsUnspecified": true }]*/
 
function foo(callback) {
    if (callback) {
        return void callback();
    }
    // no return statement
}
 
function bar(condition) {
    if (condition) {
        return undefined;
    }
    // no return statement
}

:::

When Not To Use It

If you want to allow functions to have different return behavior depending on code branching, then it is safe to disable this rule. Source: http://eslint.org/docs/rules/

title: no-cond-assign ruletype: problem relatedrules:

- no-extra-parens

In conditional statements, it is very easy to mistype a comparison operator (such as ==) as an assignment operator (such as =). For example:

// Check the user's job title
if (user.jobTitle = "manager") {
    // user.jobTitle is now incorrect
}

There are valid reasons to use assignment operators in conditional statements. However, it can be difficult to tell whether a specific assignment was intentional.

Rule Details

This rule disallows ambiguous assignment operators in test conditions of if, for, while, and do...while statements.

Options

This rule has a string option:

• "except-parens" (default) allows assignments in test conditions only if they are enclosed in parentheses (for example, to allow reassigning a variable in the test of a while or do...while loop)
• "always" disallows all assignments in test conditions

except-parens

Examples of incorrect code for this rule with the default "except-parens" option:

::: incorrect

/*eslint no-cond-assign: "error"*/
 
// Unintentional assignment
var x;
if (x = 0) {
    var b = 1;
}
 
// Practical example that is similar to an error
function setHeight(someNode) {
    "use strict";
    do {
        someNode.height = "100px";
    } while (someNode = someNode.parentNode);
}

:::

Examples of correct code for this rule with the default "except-parens" option:

::: correct

/*eslint no-cond-assign: "error"*/
 
// Assignment replaced by comparison
var x;
if (x === 0) {
    var b = 1;
}
 
// Practical example that wraps the assignment in parentheses
function setHeight(someNode) {
    "use strict";
    do {
        someNode.height = "100px";
    } while ((someNode = someNode.parentNode));
}
 
// Practical example that wraps the assignment and tests for 'null'
function setHeight(someNode) {
    "use strict";
    do {
        someNode.height = "100px";
    } while ((someNode = someNode.parentNode) !== null);
}

:::

always

Examples of incorrect code for this rule with the "always" option:

::: incorrect

/*eslint no-cond-assign: ["error", "always"]*/
 
// Unintentional assignment
var x;
if (x = 0) {
    var b = 1;
}
 
// Practical example that is similar to an error
function setHeight(someNode) {
    "use strict";
    do {
        someNode.height = "100px";
    } while (someNode = someNode.parentNode);
}
 
// Practical example that wraps the assignment in parentheses
function setHeight(someNode) {
    "use strict";
    do {
        someNode.height = "100px";
    } while ((someNode = someNode.parentNode));
}
 
// Practical example that wraps the assignment and tests for 'null'
function setHeight(someNode) {
    "use strict";
    do {
        someNode.height = "100px";
    } while ((someNode = someNode.parentNode) !== null);
}

:::

Examples of correct code for this rule with the "always" option:

::: correct

/*eslint no-cond-assign: ["error", "always"]*/
 
// Assignment replaced by comparison
var x;
if (x === 0) {
    var b = 1;
}

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

For more information visit Source: http://eslint.org/docs/rules/