huridocs/uwazi

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

title: no-console ruletype: suggestion relatedrules: - no-alert

- no-debugger

In JavaScript that is designed to be executed in the browser, it's considered a best practice to avoid using methods on console. Such messages are considered to be for debugging purposes and therefore not suitable to ship to the client. In general, calls using console should be stripped before being pushed to production.

console.log("Made it here.");
console.error("That shouldn't have happened.");

Rule Details

This rule disallows calls or assignments to methods of the console object.

Examples of incorrect code for this rule:

::: incorrect

/* eslint no-console: "error" */
 
console.log("Log a debug level message.");
console.warn("Log a warn level message.");
console.error("Log an error level message.");
console.log = foo();

:::

Examples of correct code for this rule:

::: correct

/* eslint no-console: "error" */
 
// custom console
Console.log("Hello world!");

:::

Options

This rule has an object option for exceptions:

• "allow" has an array of strings which are allowed methods of the console object

Examples of additional correct code for this rule with a sample { "allow": ["warn", "error"] } option:

::: correct

/* eslint no-console: ["error", { allow: ["warn", "error"] }] */
 
console.warn("Log a warn level message.");
console.error("Log an error level message.");

:::

When Not To Use It

If you're using Node.js, however, console is used to output information to the user and so is not strictly used for debugging purposes. If you are developing for Node.js then you most likely do not want this rule enabled.

Another case where you might not use this rule is if you want to enforce console calls and not console overwrites. For example:

/* eslint no-console: ["error", { allow: ["warn"] }] */
console.error = function (message) {
  throw new Error(message);
};

With the no-console rule in the above example, ESLint will report an error. For the above example, you can disable the rule:

// eslint-disable-next-line no-console
console.error = function (message) {
  throw new Error(message);
};
 
// or
 
console.error = function (message) {  // eslint-disable-line no-console
  throw new Error(message);
};

However, you might not want to manually add eslint-disable-next-line or eslint-disable-line. You can achieve the effect of only receiving errors for console calls with the no-restricted-syntax rule:

{
    "rules": {
        "no-console": "off",
        "no-restricted-syntax": [
            "error",
            {
                "selector": "CallExpression[callee.object.name='console'][callee.property.name!=/^(log|warn|error|info|trace)$/]",
                "message": "Unexpected property on console object was called"
            }
        ]
    }
}

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

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

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

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

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

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

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

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

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

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

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

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

title: no-console ruletype: suggestion relatedrules: - no-alert

- no-debugger

In JavaScript that is designed to be executed in the browser, it's considered a best practice to avoid using methods on console. Such messages are considered to be for debugging purposes and therefore not suitable to ship to the client. In general, calls using console should be stripped before being pushed to production.

console.log("Made it here.");
console.error("That shouldn't have happened.");

Rule Details

This rule disallows calls or assignments to methods of the console object.

Examples of incorrect code for this rule:

::: incorrect

/* eslint no-console: "error" */
 
console.log("Log a debug level message.");
console.warn("Log a warn level message.");
console.error("Log an error level message.");
console.log = foo();

:::

Examples of correct code for this rule:

::: correct

/* eslint no-console: "error" */
 
// custom console
Console.log("Hello world!");

:::

Options

This rule has an object option for exceptions:

• "allow" has an array of strings which are allowed methods of the console object

Examples of additional correct code for this rule with a sample { "allow": ["warn", "error"] } option:

::: correct

/* eslint no-console: ["error", { allow: ["warn", "error"] }] */
 
console.warn("Log a warn level message.");
console.error("Log an error level message.");

:::

When Not To Use It

If you're using Node.js, however, console is used to output information to the user and so is not strictly used for debugging purposes. If you are developing for Node.js then you most likely do not want this rule enabled.

Another case where you might not use this rule is if you want to enforce console calls and not console overwrites. For example:

/* eslint no-console: ["error", { allow: ["warn"] }] */
console.error = function (message) {
  throw new Error(message);
};

With the no-console rule in the above example, ESLint will report an error. For the above example, you can disable the rule:

// eslint-disable-next-line no-console
console.error = function (message) {
  throw new Error(message);
};
 
// or
 
console.error = function (message) {  // eslint-disable-line no-console
  throw new Error(message);
};

However, you might not want to manually add eslint-disable-next-line or eslint-disable-line. You can achieve the effect of only receiving errors for console calls with the no-restricted-syntax rule:

{
    "rules": {
        "no-console": "off",
        "no-restricted-syntax": [
            "error",
            {
                "selector": "CallExpression[callee.object.name='console'][callee.property.name!=/^(log|warn|error|info|trace)$/]",
                "message": "Unexpected property on console object was called"
            }
        ]
    }
}

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

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

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

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

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

For more information visit 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/