Disallow the type conversion with shorter notations. (no-implicit-coercion)

禁止使用较短的符号实现类型转换 (no-implicit-coercion)

The --fix option on the command line can automatically fix some of the problems reported by this rule.

命令行中的 --fix 选项可以自动修复一些该规则报告的问题。

In JavaScript, there are a lot of different ways to convert value types. Some of them might be hard to read and understand.

在 JavaScript 中，有许多不同的方式进行类型转换。其中有些可能难于阅读和理解。

Such as:

例如：

var b = !!foo;
var b = ~foo.indexOf(".");
var n = +foo;
var n = 1 * foo;
var s = "" + foo;
foo += ``;

Those can be replaced with the following code:

可以使用下面的代码替换:

var b = Boolean(foo);
var b = foo.indexOf(".") !== -1;
var n = Number(foo);
var n = Number(foo);
var s = String(foo);
foo = String(foo);

Rule Details

This rule is aimed to flag shorter notations for the type conversion, then suggest a more self-explanatory notation.

该规则目的是标记出使用较短的符号进行类型转换的情况，建议使用一个更明确的符号。

Options

This rule has three main options and one override option to allow some coercions as required.

该规则有三个主要选项和一个覆盖选项，覆盖选项允许一些强制要求。

• "boolean" (true by default) - When this is true, this rule warns shorter type conversions for boolean type.
• "boolean"(默认是 true)－当为 true 时，规则会对简短的 boolean 类型转换发出警告。
• "number" (true by default) - When this is true, this rule warns shorter type conversions for number type.
• "number"(默认是 true)－当为 true 时，规则会对简短的 number 类型转换发出警告。
• "string" (true by default) - When this is true, this rule warns shorter type conversions for string type.
• "string"(默认是 true)－当为 true 时，规则会对简短的 string 类型转换发出警告。
• "allow" (empty by default) - Each entry in this array can be one of ~, !!, + or * that are to be allowed.
• "allow" (默认是 empty) - 这个数组的每一项可以是 ~、!!、+ 或 *。

Note that operator + in allow list would allow +foo (number coercion) as well as "" + foo (string coercion).

注意，在 allow 列表中，操作符 + 同时允许 +foo（数字）和 "" + foo (字符串)

boolean

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

默认选项 { "boolean": true } 的 错误 代码示例：

/*eslint no-implicit-coercion: "error"*/

var b = !!foo;
var b = ~foo.indexOf(".");
// bitwise not is incorrect only with `indexOf`/`lastIndexOf` method calling.

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

默认选项 { "boolean": true } 的 正确 代码示例：

/*eslint no-implicit-coercion: "error"*/

var b = Boolean(foo);
var b = foo.indexOf(".") !== -1;

var n = ~foo; // This is a just bitwise not.

number

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

默认选项 { "number": true } 的 错误 代码示例：

/*eslint no-implicit-coercion: "error"*/

var n = +foo;
var n = 1 * foo;

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

默认选项 { "number": true } 的 正确 代码示例：

/*eslint no-implicit-coercion: "error"*/

var n = Number(foo);
var n = parseFloat(foo);
var n = parseInt(foo, 10);

string

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

默认选项 { "string": true } 的 错误 代码示例：

/*eslint no-implicit-coercion: "error"*/

var s = "" + foo;
var s = `` + foo;
foo += "";
foo += ``;

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

默认选项 { "string": true } 的 正确 代码示例：

/*eslint no-implicit-coercion: "error"*/

var s = String(foo);
foo = String(foo);

allow

Using allow list, we can override and allow specific operators.

使用 allow 列表，我们可以覆盖和允许特定的操作符。

Examples of correct code for the sample { "allow": ["!!", "~"] } option:

默认选项 { "allow": ["!!", "~"] } 的 正确 代码示例：

/*eslint no-implicit-coercion: [2, { "allow": ["!!", "~"] } ]*/

var b = !!foo;
var b = ~foo.indexOf(".");

When Not To Use It

If you don’t want to be notified about shorter notations for the type conversion, you can safely disable this rule.

如果你不想收到关于使用较短符号进行类型转换的通知，可以禁用此规则。

Version

This rule was introduced in ESLint 1.0.0-rc-2.

该规则在 ESLint 1.0.0-rc-2 中被引入。

Resources

• Rule source
• Documentation source