disallow assignment operators in conditional statements (no-cond-assign)

禁止在条件语句中出现赋值操作符（no-cond-assign）

The "extends": "eslint:recommended" property in a configuration file enables this rule.

配置文件中的 "extends": "eslint:recommended" 属性启用了此规则。

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

在条件语句中，很容易将一个比较运算符（像 ==）错写成赋值运算符（如 =）。例如：

// 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.

在条件语句中使用赋值操作符是有效的。然而，很难判断某个特定的赋值是否是有意为之。

Rule Details

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

该规则禁止在 if、for、while 和 do...while 语句中出现模棱两可的赋值操作符。

Options

This rule has a string option:

该规则有一个字符串选项：

except-parens

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

默认选项 "except-parens" 的 错误 代码示例：

/*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:

默认选项 "except-parens" 的 正确 代码示例：

/*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:

选项 "always" 的 错误 代码示例：

/*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:

选项 "always" 的 正确 代码示例：

/*eslint no-cond-assign: ["error", "always"]*/

// Assignment replaced by comparison
var x;
if (x === 0) {
    var b = 1;
}

Version

This rule was introduced in ESLint 0.0.9.

该规则在 ESLint 0.0.9 中被引入。

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