no-cond-assign
Disallow assignment operators in conditional expressions
✅ Recommended
The "extends": "eslint:recommended" property in a configuration file enables this rule
在条件语句中，很容易把比较运算符（如 ==）误打成赋值运算符（如 =）。比如：
// 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理由的。然而，要想知道一个特定赋值是不是故意的就很难。
规则细节
使用此规则禁用 if、for、while 和 do...while 测试条件中的模糊赋值运算符。
选项
此规则选项为字符串：
"except-parens"（默认值）只有当它们被括号括住时才允许测试条件中的赋值（例如，允许在while或do...while循环测试中重新赋值变量）。"always"不允许在测试条件中进行任意赋值
except-parens
使用此规则与默认的 "except-parens" 选项的错误示例：
Open in Playground
/*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);
}
使用此规则与默认的 "except-parens" 选项的正确示例：
Open in Playground
/*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
使用此规则与 "always" 选项的错误示例：
Open in Playground
/*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);
}
使用此规则与 "always" 选项的正确示例：
Open in Playground
/*eslint no-cond-assign: ["error", "always"]*/
// Assignment replaced by comparison
var x;
if (x === 0) {
var b = 1;
}
Related Rules
Version
This rule was introduced in ESLint v0.0.9.