Rule to disallow a duplicate case label (no-duplicate-case)

禁止重复 case 标签（no-duplicate-case）

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。

If a switch statement has duplicate test expressions in case clauses, it is likely that a programmer copied a case clause but forgot to change the test expression.

如果一个 switch 语句中的 case 子句中出现重复的测试表达式，那么很有可能是某个程序员拷贝了一个 case 子句但忘记了修改测试表达式。

Rule Details

This rule disallows duplicate test expressions in case clauses of switch statements.

该规则禁止在 switch 语句中的 case 子句中出现重复的测试表达式。

Examples of incorrect code for this rule:

错误 代码示例：

/*eslint no-duplicate-case: "error"*/

var a = 1,
    one = 1;

switch (a) {
    case 1:
        break;
    case 2:
        break;
    case 1:         // duplicate test expression
        break;
    default:
        break;
}

switch (a) {
    case one:
        break;
    case 2:
        break;
    case one:         // duplicate test expression
        break;
    default:
        break;
}

switch (a) {
    case "1":
        break;
    case "2":
        break;
    case "1":         // duplicate test expression
        break;
    default:
        break;
}

Examples of correct code for this rule:

正确 代码示例：

/*eslint no-duplicate-case: "error"*/

var a = 1,
    one = 1;

switch (a) {
    case 1:
        break;
    case 2:
        break;
    case 3:
        break;
    default:
        break;
}

switch (a) {
    case one:
        break;
    case 2:
        break;
    case 3:
        break;
    default:
        break;
}

switch (a) {
    case "1":
        break;
    case "2":
        break;
    case "3":
        break;
    default:
        break;
}

Version

This rule was introduced in ESLint 0.17.0.

该规则在 ESLint 0.17.0 中被引入。

Resources