no-fallthrough

不允许 case 语句的失败

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

JavaScript 中的 switch 语句是该语言中更容易出错的结构之一，这部分归功于 "fall through" 从一个 case 到另一个的能力。例如：

switch(foo) {
    case 1:
        doSomething();

    case 2:
        doSomethingElse();
}

在此示例中，如果 foo 是 1，则执行将流经这两种情况，因为第一种情况会一直到第二种情况。您可以通过使用 break 来防止这种情况，如下例所示：

switch(foo) {
    case 1:
        doSomething();
        break;

    case 2:
        doSomethingElse();
}

当您不想要失败时，这很好用，但如果失败是故意的，则无法在语言中表明这一点。最好的做法是始终使用与 /falls?\s?through/i 正则表达式匹配但不是指令的注释来指示何时有意进行失败：

switch(foo) {
    case 1:
        doSomething();
        // falls through

    case 2:
        doSomethingElse();
}

switch(foo) {
    case 1:
        doSomething();
        // fall through

    case 2:
        doSomethingElse();
}

switch(foo) {
    case 1:
        doSomething();
        // fallsthrough

    case 2:
        doSomethingElse();
}

switch(foo) {
    case 1: {
        doSomething();
        // falls through
    }

    case 2: {
        doSomethingElse();
    }
}

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规则详情

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Wk+Mu7oFIccqpNSe5orR05ZG/BDV40hHIKzF0SoJnVcuS8r6evQjx3oyoFn9+fZT

/*eslint no-fallthrough: "error"*/

switch(foo) {
    case 1:
        doSomething();

    case 2:
        doSomething();
}

UubGaThNGVSAZCEeqgdAAx/QE1uwW/De5ytjPBnKCKqeOsDZpJS0MvQSJQtY0WPI

/*eslint no-fallthrough: "error"*/

switch(foo) {
    case 1:
        doSomething();
        break;

    case 2:
        doSomething();
}

function bar(foo) {
    switch(foo) {
        case 1:
            doSomething();
            return;

        case 2:
            doSomething();
    }
}

switch(foo) {
    case 1:
        doSomething();
        throw new Error("Boo!");

    case 2:
        doSomething();
}

switch(foo) {
    case 1:
    case 2:
        doSomething();
}

switch(foo) {
    case 1:
        doSomething();
        // falls through

    case 2:
        doSomething();
}

switch(foo) {
    case 1: {
        doSomething();
        // falls through
    }

    case 2: {
        doSomethingElse();
    }
}

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选项

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commentPattern

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/*eslint no-fallthrough: ["error", { "commentPattern": "break[\\s\\w]*omitted" }]*/

switch(foo) {
    case 1:
        doSomething();
        // break omitted

    case 2:
        doSomething();
}

switch(foo) {
    case 1:
        doSomething();
        // caution: break is omitted intentionally

    default:
        doSomething();
}

allowEmptyCase

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/* eslint no-fallthrough: ["error", { "allowEmptyCase": true }] */

switch(foo){
    case 1:

    case 2: doSomething();
}

switch(foo){
    case 1:
    /*
    Put a message here 
    */
    case 2: doSomething();
}

何时不使用

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