Do not warn if .flat() has more than one parameter or if the one pa…

…rameter is not `1` (#317)
sindresorhus · Jun 10, 2019 · 6f10722 · 6f10722
1 parent 1e3bb8f
commit 6f10722
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diff --git a/rules/prefer-flat-map.js b/rules/prefer-flat-map.js
@@ -98,6 +98,14 @@ const create = context => ({
 			return;
 		}
 
+		if (node.arguments.length > 1) {
+			return;
+		}
+
+		if (node.arguments.length === 1 && node.arguments[0].type === 'Literal' && node.arguments[0].value !== 1) {
+			return;
+		}
+
 		const parent = node.callee.object;
 
 		if (!isMethodNamed(parent, 'map')) {

diff --git a/test/prefer-flat-map.js b/test/prefer-flat-map.js
@@ -26,7 +26,9 @@ ruleTester.run('prefer-flat-map', rule, {
 		outdent`
 			let bar = [1,2,3].map(i => [i]);
 			bar = bar.flat();
-		`
+		`,
+		'const bar = [[1],[2],[3]].map(i => [i]).flat(2)',
+		'const bar = [[1],[2],[3]].map(i => [i]).flat(1, null)'
 	],
 	invalid: [
 		{
@@ -157,6 +159,11 @@ ruleTester.run('prefer-flat-map', rule, {
 			output: 'let bar = [1,2,3] . flatMap( x => y )  // 🤪',
 			errors: [error]
 		},
+		{
+			code: 'const bar = [1,2,3].map(i => [i]).flat(1);',
+			output: 'const bar = [1,2,3].flatMap(i => [i]);',
+			errors: [error]
+		},
 		{
 			code: outdent`
 				const foo = bars