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fiskersindresorhus
fisker
and
sindresorhus
authoredJan 30, 2025··
Add consistent-date-clone rule (#2544)
Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>
·
v58.0.0v57.0.0
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‎docs/rules/consistent-date-clone.md

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# Prefer passing `Date` directly to the constructor when cloning
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💼 This rule is enabled in the ✅ `recommended` [config](https://github.com/sindresorhus/eslint-plugin-unicorn#preset-configs-eslintconfigjs).
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🔧 This rule is automatically fixable by the [`--fix` CLI option](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix).
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<!-- end auto-generated rule header -->
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<!-- Do not manually modify this header. Run: `npm run fix:eslint-docs` -->
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The [`Date` constructor](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/Date) can clone a `⁠Date` object directly when passed as an argument, making timestamp conversion unnecessary.
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> Note: Before ES2015, `new Date(date)` converted `date` to a string first, so it's not safe to clone.
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## Examples
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```js
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// ❌
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new Date(date.getTime());
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// ✅
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new Date(date);
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```

‎readme.md

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| [better-regex](docs/rules/better-regex.md) | Improve regexes by making them shorter, consistent, and safer. | | 🔧 | |
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| [catch-error-name](docs/rules/catch-error-name.md) | Enforce a specific parameter name in catch clauses. | ✅ | 🔧 | |
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| [consistent-assert](docs/rules/consistent-assert.md) | Enforce consistent assertion style with `node:assert`. | ✅ | 🔧 | |
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| [consistent-date-clone](docs/rules/consistent-date-clone.md) | Prefer passing `Date` directly to the constructor when cloning. | ✅ | 🔧 | |
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| [consistent-destructuring](docs/rules/consistent-destructuring.md) | Use destructured variables over properties. | | 🔧 | 💡 |
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| [consistent-empty-array-spread](docs/rules/consistent-empty-array-spread.md) | Prefer consistent types when spreading a ternary in an array literal. | ✅ | 🔧 | |
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| [consistent-existence-index-check](docs/rules/consistent-existence-index-check.md) | Enforce consistent style for element existence checks with `indexOf()`, `lastIndexOf()`, `findIndex()`, and `findLastIndex()`. | ✅ | 🔧 | |

‎rules/consistent-date-clone.js

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import {isMethodCall, isNewExpression} from './ast/index.js';
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import {removeMethodCall} from './fix/index.js';
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const MESSAGE_ID_ERROR = 'consistent-date-clone/error';
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const messages = {
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[MESSAGE_ID_ERROR]: 'Unnecessary `.getTime()` call.',
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};
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/** @param {import('eslint').Rule.RuleContext} context */
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const create = context => ({
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NewExpression(newExpression) {
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if (!isNewExpression(newExpression, {name: 'Date', argumentsLength: 1})) {
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return;
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}
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const [callExpression] = newExpression.arguments;
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if (!isMethodCall(callExpression, {
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method: 'getTime',
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argumentsLength: 0,
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optionalCall: false,
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optionalMember: false,
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})) {
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return;
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}
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return {
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node: callExpression,
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loc: {start: callExpression.callee.property.loc.start, end: callExpression.loc.end},
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messageId: MESSAGE_ID_ERROR,
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fix: fixer => removeMethodCall(fixer, callExpression, context.sourceCode),
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};
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},
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});
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/** @type {import('eslint').Rule.RuleModule} */
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const config = {
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create,
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meta: {
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type: 'suggestion',
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docs: {
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description: 'Prefer passing `Date` directly to the constructor when cloning.',
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recommended: true,
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},
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fixable: 'code',
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messages,
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},
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};
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export default config;

‎rules/index.js

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import betterRegex from './better-regex.js';
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import catchErrorName from './catch-error-name.js';
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import consistentAssert from './consistent-assert.js';
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import consistentDateClone from './consistent-date-clone.js';
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import consistentDestructuring from './consistent-destructuring.js';
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import consistentEmptyArraySpread from './consistent-empty-array-spread.js';
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import consistentExistenceIndexCheck from './consistent-existence-index-check.js';
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'better-regex': createRule(betterRegex, 'better-regex'),
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'catch-error-name': createRule(catchErrorName, 'catch-error-name'),
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'consistent-assert': createRule(consistentAssert, 'consistent-assert'),
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'consistent-date-clone': createRule(consistentDateClone, 'consistent-date-clone'),
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'consistent-destructuring': createRule(consistentDestructuring, 'consistent-destructuring'),
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'consistent-empty-array-spread': createRule(consistentEmptyArraySpread, 'consistent-empty-array-spread'),
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'consistent-existence-index-check': createRule(consistentExistenceIndexCheck, 'consistent-existence-index-check'),

‎test/consistent-date-clone.js

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import outdent from 'outdent';
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import {getTester} from './utils/test.js';
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const {test} = getTester(import.meta);
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test.snapshot({
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valid: [
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'new Date(date)',
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'date.getTime()',
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'new Date(...date.getTime())',
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'new Date(getTime())',
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'new Date(date.getTime(), extraArgument)',
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'new Date(date.not_getTime())',
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'new Date(date?.getTime())',
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'new NotDate(date.getTime())',
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'new Date(date[getTime]())',
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'new Date(date.getTime(extraArgument))',
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'Date(date.getTime())',
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// We may support these cases in future, https://github.com/sindresorhus/eslint-plugin-unicorn/issues/2437
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outdent`
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new Date(
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date.getFullYear(),
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date.getMonth(),
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date.getDate(),
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date.getHours(),
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date.getMinutes(),
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date.getSeconds(),
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date.getMilliseconds(),
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);
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`,
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outdent`
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new Date(
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date.getFullYear(),
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date.getMonth(),
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date.getDate(),
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date.getHours(),
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date.getMinutes(),
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date.getSeconds(),
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);
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`,
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],
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invalid: [
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'new Date(date.getTime())',
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'new Date(date.getTime(),)',
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'new Date((0, date).getTime())',
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'new Date(date.getTime(/* comment */))',
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'new Date(date./* comment */getTime())',
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],
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});

‎test/package.js

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'no-named-default',
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'consistent-assert',
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'no-accessor-recursion',
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'consistent-date-clone',
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]);
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test('Every rule is defined in index file in alphabetical order', t => {

‎test/snapshots/consistent-date-clone.js.md

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# Snapshot report for `test/consistent-date-clone.js`
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The actual snapshot is saved in `consistent-date-clone.js.snap`.
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Generated by [AVA](https://avajs.dev).
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## invalid(1): new Date(date.getTime())
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> Input
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`␊
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1 | new Date(date.getTime())␊
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`
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> Output
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`␊
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1 | new Date(date)␊
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`
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> Error 1/1
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`␊
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> 1 | new Date(date.getTime())␊
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| ^^^^^^^^^ Unnecessary \`.getTime()\` call.␊
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`
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## invalid(2): new Date(date.getTime(),)
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> Input
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`␊
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1 | new Date(date.getTime(),)␊
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`
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> Output
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`␊
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1 | new Date(date,)␊
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`
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> Error 1/1
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`␊
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> 1 | new Date(date.getTime(),)␊
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| ^^^^^^^^^ Unnecessary \`.getTime()\` call.␊
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`
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## invalid(3): new Date((0, date).getTime())
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> Input
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`␊
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1 | new Date((0, date).getTime())␊
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`
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> Output
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`␊
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1 | new Date((0, date))␊
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`
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> Error 1/1
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`␊
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> 1 | new Date((0, date).getTime())␊
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| ^^^^^^^^^ Unnecessary \`.getTime()\` call.␊
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`
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## invalid(4): new Date(date.getTime(/* comment */))
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> Input
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`␊
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1 | new Date(date.getTime(/* comment */))␊
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`
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> Output
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`␊
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1 | new Date(date)␊
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`
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> Error 1/1
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`␊
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> 1 | new Date(date.getTime(/* comment */))␊
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| ^^^^^^^^^^^^^^^^^^^^^^ Unnecessary \`.getTime()\` call.␊
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`
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## invalid(5): new Date(date./* comment */getTime())
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> Input
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`␊
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1 | new Date(date./* comment */getTime())␊
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`
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> Output
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`␊
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1 | new Date(date)␊
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`
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> Error 1/1
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`␊
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> 1 | new Date(date./* comment */getTime())␊
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| ^^^^^^^^^ Unnecessary \`.getTime()\` call.␊
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`

‎test/snapshots/consistent-date-clone.js.snap

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