no-cond-assign

禁止条件表达式中的赋值运算符

配置文件 中的 "extends": "eslint:recommended" 属性启用了该规则

在条件语句中，很容易将比较运算符（例如 ==）误键入为赋值运算符（例如 =）。例如：

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

在条件语句中使用赋值运算符是有充分理由的。然而，很难判断一个特定的任务是否是故意的。

规则详情

此规则不允许在 if、for、while 和 do...while 语句的测试条件中使用模棱两可的赋值运算符。

选项

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except-parens

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/*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);
}

IkNtK1AnBCO6NSjlzxSStf5iVpMs1HDgZdtYG1DAvezN42FPqvNavN7MY6FVJKytzEOE1zGwbAxrglUrdqMES2D6yuhLZF+e0hP6dckWOe2jDs1LqpQY2IRpOJEiR3hu

/*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

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/*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);
}

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

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