comma-dangle

要求或不允许尾随逗号

一些该规则报告的问题可以通过 --fix 命令行选项 自动修复

根据 ECMAScript 5（和 ECMAScript 3！）规范，对象字面中的尾随逗号是有效的。但是，IE8（不在 IE8 文档模式下）及以下版本在遇到 JavaScript 中的尾随逗号时会抛出错误。

var foo = {
    bar: "baz",
    qux: "quux",
};

尾随逗号简化了向对象和数组添加和删除项目，因为只有您正在修改的行必须被触及。支持尾随逗号的另一个论点是，当从对象或数组中添加或删除项目时，它提高了差异的清晰度：

不太晰：

 var foo = {
-    bar: "baz",
-    qux: "quux"
+    bar: "baz"
 };

y+6UrFn0OjSkxebtp/pStA==

 var foo = {
     bar: "baz",
-    qux: "quux",
 };

规则详情

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选项

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{
    "comma-dangle": ["error", "never"],
    // or
    "comma-dangle": ["error", {
        "arrays": "never",
        "objects": "never",
        "imports": "never",
        "exports": "never",
        "functions": "never"
    }]
}

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never

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/*eslint comma-dangle: ["error", "never"]*/

var foo = {
    bar: "baz",
    qux: "quux",
};

var arr = [1,2,];

foo({
  bar: "baz",
  qux: "quux",
});

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/*eslint comma-dangle: ["error", "never"]*/

var foo = {
    bar: "baz",
    qux: "quux"
};

var arr = [1,2];

foo({
  bar: "baz",
  qux: "quux"
});

always

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/*eslint comma-dangle: ["error", "always"]*/

var foo = {
    bar: "baz",
    qux: "quux"
};

var arr = [1,2];

foo({
  bar: "baz",
  qux: "quux"
});

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/*eslint comma-dangle: ["error", "always"]*/

var foo = {
    bar: "baz",
    qux: "quux",
};

var arr = [1,2,];

foo({
  bar: "baz",
  qux: "quux",
});

always-multiline

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/*eslint comma-dangle: ["error", "always-multiline"]*/

var foo = {
    bar: "baz",
    qux: "quux"
};

var foo = { bar: "baz", qux: "quux", };

var arr = [1,2,];

var arr = [1,
    2,];

var arr = [
    1,
    2
];

foo({
  bar: "baz",
  qux: "quux"
});

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/*eslint comma-dangle: ["error", "always-multiline"]*/

var foo = {
    bar: "baz",
    qux: "quux",
};

var foo = {bar: "baz", qux: "quux"};
var arr = [1,2];

var arr = [1,
    2];

var arr = [
    1,
    2,
];

foo({
  bar: "baz",
  qux: "quux",
});

only-multiline

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/*eslint comma-dangle: ["error", "only-multiline"]*/

var foo = { bar: "baz", qux: "quux", };

var arr = [1,2,];

var arr = [1,
    2,];

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/*eslint comma-dangle: ["error", "only-multiline"]*/

var foo = {
    bar: "baz",
    qux: "quux",
};

var foo = {
    bar: "baz",
    qux: "quux"
};

var foo = {bar: "baz", qux: "quux"};
var arr = [1,2];

var arr = [1,
    2];

var arr = [
    1,
    2,
];

var arr = [
    1,
    2
];

foo({
  bar: "baz",
  qux: "quux",
});

foo({
  bar: "baz",
  qux: "quux"
});

functions

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/*eslint comma-dangle: ["error", {"functions": "never"}]*/

function foo(a, b,) {
}

foo(a, b,);
new foo(a, b,);

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/*eslint comma-dangle: ["error", {"functions": "never"}]*/

function foo(a, b) {
}

foo(a, b);
new foo(a, b);

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/*eslint comma-dangle: ["error", {"functions": "always"}]*/

function foo(a, b) {
}

foo(a, b);
new foo(a, b);

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/*eslint comma-dangle: ["error", {"functions": "always"}]*/

function foo(a, b,) {
}

foo(a, b,);
new foo(a, b,);

何时不使用

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