eslint-plugin-unicorn/rules/prefer-date-now.js

Various awesome ESLint rules

'use strict';
const {
	matches,
	methodCallSelector,
	newExpressionSelector,
	callExpressionSelector
} = require('./selectors/index.js');

const MESSAGE_ID_DEFAULT = 'prefer-date';
const MESSAGE_ID_METHOD = 'prefer-date-now-over-methods';
const MESSAGE_ID_NUMBER = 'prefer-date-now-over-number-data-object';
const messages = {
	[MESSAGE_ID_DEFAULT]: 'Prefer `Date.now()` over `new Date()`.',
	[MESSAGE_ID_METHOD]: 'Prefer `Date.now()` over `Date#{{method}}()`.',
	[MESSAGE_ID_NUMBER]: 'Prefer `Date.now()` over `Number(new Date())`.'
};

const createNewDateSelector = path => newExpressionSelector({path, name: 'Date', length: 0});
const operatorsSelector = (...operators) => matches(operators.map(operator => `[operator="${operator}"]`));
// `new Date()`
const newDateSelector = createNewDateSelector();
// `new Date().{getTime,valueOf}()`
const methodsSelector = [
	methodCallSelector({
		names: ['getTime', 'valueOf'],
		length: 0
	}),
	createNewDateSelector('callee.object')
].join('');
// `{Number,BigInt}(new Date())`
const builtinObjectSelector = [
	callExpressionSelector({names: ['Number', 'BigInt'], length: 1}),
	createNewDateSelector('arguments.0')
].join('');
// https://github.com/estree/estree/blob/master/es5.md#unaryoperator
const unaryExpressionsSelector = [
	'UnaryExpression',
	operatorsSelector('+', '-'),
	createNewDateSelector('argument')
].join('');
const assignmentExpressionSelector = [
	'AssignmentExpression',
	operatorsSelector('-=', '*=', '/=', '%=', '**='),
	'>',
	`${newDateSelector}.right`
].join('');
const binaryExpressionSelector = [
	'BinaryExpression',
	operatorsSelector('-', '*', '/', '%', '**'),
	// Both `left` and `right` properties
	'>',
	newDateSelector
].join('');

const getProblem = (node, problem) => ({
	node,
	messageId: MESSAGE_ID_DEFAULT,
	fix: fixer => fixer.replaceText(node, 'Date.now()'),
	...problem
});

const create = () => {
	return {
		[methodsSelector](node) {
			const method = node.callee.property;
			return getProblem(node, {
				node: method,
				messageId: MESSAGE_ID_METHOD,
				data: {method: method.name}
			});
		},
		[builtinObjectSelector](node) {
			const {name} = node.callee;
			if (name === 'Number') {
				return getProblem(node, {
					messageId: MESSAGE_ID_NUMBER
				});
			}

			return getProblem(node.arguments[0]);
		},
		[unaryExpressionsSelector](node) {
			return getProblem(node.operator === '-' ? node.argument : node);
		},
		[assignmentExpressionSelector](node) {
			return getProblem(node);
		},
		[binaryExpressionSelector](node) {
			return getProblem(node);
		}
	};
};

module.exports = {
	create,
	meta: {
		type: 'suggestion',
		docs: {
			description: 'Prefer `Date.now()` to get the number of milliseconds since the Unix Epoch.'
		},
		fixable: 'code',
		messages
	}
};