biomejs · Netail · Nov 14, 2025 · Nov 14, 2025 · Nov 14, 2025
diff --git a/.changeset/all-kiwis-poke.md b/.changeset/all-kiwis-poke.md
@@ -0,0 +1,13 @@
+---
+"@biomejs/biome": patch
+---
+
+Added the nursery rule [`useFind`](https://biomejs.dev/linter/rules/use-find/). Enforce the use of Array.prototype.find() over Array.prototype.filter() followed by [0] when looking for a single result.
+
+**Invalid:**
+
+```js
+[1, 2, 3].filter(x => x > 1)[0];
+
+[1, 2, 3].filter(x => x > 1).at(0);
+```
diff --git a/crates/biome_cli/src/execute/migrate/eslint_any_rule_to_biome.rs b/crates/biome_cli/src/execute/migrate/eslint_any_rule_to_biome.rs
diff --git a/crates/biome_configuration/src/analyzer/linter/rules.rs b/crates/biome_configuration/src/analyzer/linter/rules.rs
diff --git a/crates/biome_configuration/src/generated/domain_selector.rs b/crates/biome_configuration/src/generated/domain_selector.rs
diff --git a/crates/biome_diagnostics_categories/src/categories.rs b/crates/biome_diagnostics_categories/src/categories.rs
@@ -203,6 +203,7 @@ define_categories! {
     "lint/nursery/useExhaustiveSwitchCases": "https://biomejs.dev/linter/rules/use-exhaustive-switch-cases",
     "lint/nursery/useExplicitFunctionReturnType": "https://biomejs.dev/linter/rules/use-explicit-type",
     "lint/nursery/useExplicitType": "https://biomejs.dev/linter/rules/use-explicit-type",
+    "lint/nursery/useFind": "https://biomejs.dev/linter/rules/use-find",
     "lint/nursery/useImportRestrictions": "https://biomejs.dev/linter/rules/use-import-restrictions",
     "lint/nursery/useJsxCurlyBraceConvention": "https://biomejs.dev/linter/rules/use-jsx-curly-brace-convention",
     "lint/nursery/useMaxParams": "https://biomejs.dev/linter/rules/use-max-params",

diff --git a/crates/biome_js_analyze/src/lint/nursery.rs b/crates/biome_js_analyze/src/lint/nursery.rs
@@ -30,11 +30,12 @@ pub mod use_array_sort_compare;
 pub mod use_consistent_arrow_return;
 pub mod use_exhaustive_switch_cases;
 pub mod use_explicit_type;
+pub mod use_find;
 pub mod use_max_params;
 pub mod use_qwik_method_usage;
 pub mod use_qwik_valid_lexical_scope;
 pub mod use_sorted_classes;
 pub mod use_spread;
 pub mod use_vue_define_macros_order;
 pub mod use_vue_multi_word_component_names;
-declare_lint_group! { pub Nursery { name : "nursery" , rules : [self :: no_continue :: NoContinue , self :: no_deprecated_imports :: NoDeprecatedImports , self :: no_empty_source :: NoEmptySource , self :: no_floating_promises :: NoFloatingPromises , self :: no_for_in :: NoForIn , self :: no_import_cycles :: NoImportCycles , self :: no_increment_decrement :: NoIncrementDecrement , self :: no_jsx_literals :: NoJsxLiterals , self :: no_misused_promises :: NoMisusedPromises , self :: no_next_async_client_component :: NoNextAsyncClientComponent , self :: no_parameters_only_used_in_recursion :: NoParametersOnlyUsedInRecursion , self :: no_react_forward_ref :: NoReactForwardRef , self :: no_shadow :: NoShadow , self :: no_unknown_attribute :: NoUnknownAttribute , self :: no_unnecessary_conditions :: NoUnnecessaryConditions , self :: no_unresolved_imports :: NoUnresolvedImports , self :: no_unused_expressions :: NoUnusedExpressions , self :: no_useless_catch_binding :: NoUselessCatchBinding , self :: no_useless_undefined :: NoUselessUndefined , self :: no_vue_data_object_declaration :: NoVueDataObjectDeclaration , self :: no_vue_duplicate_keys :: NoVueDuplicateKeys , self :: no_vue_reserved_keys :: NoVueReservedKeys , self :: no_vue_reserved_props :: NoVueReservedProps , self :: use_array_sort_compare :: UseArraySortCompare , self :: use_consistent_arrow_return :: UseConsistentArrowReturn , self :: use_exhaustive_switch_cases :: UseExhaustiveSwitchCases , self :: use_explicit_type :: UseExplicitType , self :: use_max_params :: UseMaxParams , self :: use_qwik_method_usage :: UseQwikMethodUsage , self :: use_qwik_valid_lexical_scope :: UseQwikValidLexicalScope , self :: use_sorted_classes :: UseSortedClasses , self :: use_spread :: UseSpread , self :: use_vue_define_macros_order :: UseVueDefineMacrosOrder , self :: use_vue_multi_word_component_names :: UseVueMultiWordComponentNames ,] } }
+declare_lint_group! { pub Nursery { name : "nursery" , rules : [self :: no_continue :: NoContinue , self :: no_deprecated_imports :: NoDeprecatedImports , self :: no_empty_source :: NoEmptySource , self :: no_floating_promises :: NoFloatingPromises , self :: no_for_in :: NoForIn , self :: no_import_cycles :: NoImportCycles , self :: no_increment_decrement :: NoIncrementDecrement , self :: no_jsx_literals :: NoJsxLiterals , self :: no_misused_promises :: NoMisusedPromises , self :: no_next_async_client_component :: NoNextAsyncClientComponent , self :: no_parameters_only_used_in_recursion :: NoParametersOnlyUsedInRecursion , self :: no_react_forward_ref :: NoReactForwardRef , self :: no_shadow :: NoShadow , self :: no_unknown_attribute :: NoUnknownAttribute , self :: no_unnecessary_conditions :: NoUnnecessaryConditions , self :: no_unresolved_imports :: NoUnresolvedImports , self :: no_unused_expressions :: NoUnusedExpressions , self :: no_useless_catch_binding :: NoUselessCatchBinding , self :: no_useless_undefined :: NoUselessUndefined , self :: no_vue_data_object_declaration :: NoVueDataObjectDeclaration , self :: no_vue_duplicate_keys :: NoVueDuplicateKeys , self :: no_vue_reserved_keys :: NoVueReservedKeys , self :: no_vue_reserved_props :: NoVueReservedProps , self :: use_array_sort_compare :: UseArraySortCompare , self :: use_consistent_arrow_return :: UseConsistentArrowReturn , self :: use_exhaustive_switch_cases :: UseExhaustiveSwitchCases , self :: use_explicit_type :: UseExplicitType , self :: use_find :: UseFind , self :: use_max_params :: UseMaxParams , self :: use_qwik_method_usage :: UseQwikMethodUsage , self :: use_qwik_valid_lexical_scope :: UseQwikValidLexicalScope , self :: use_sorted_classes :: UseSortedClasses , self :: use_spread :: UseSpread , self :: use_vue_define_macros_order :: UseVueDefineMacrosOrder , self :: use_vue_multi_word_component_names :: UseVueMultiWordComponentNames ,] } }
diff --git a/crates/biome_js_analyze/src/lint/nursery/use_find.rs b/crates/biome_js_analyze/src/lint/nursery/use_find.rs
@@ -0,0 +1,120 @@
+use biome_analyze::{
+    Rule, RuleDiagnostic, RuleDomain, RuleSource, context::RuleContext, declare_lint_rule,
+};
+use biome_console::markup;
+use biome_js_syntax::{
+    AnyJsExpression, JsCallExpression, JsComputedMemberExpression, JsStaticMemberExpression,
+};
+use biome_rowan::{AstNode, AstSeparatedList, TextRange};
+use biome_rule_options::use_find::UseFindOptions;
+
+use crate::services::typed::Typed;
+
+declare_lint_rule! {
+    /// Enforce the use of Array.prototype.find() over Array.prototype.filter() followed by [0] when looking for a single result.
+    ///
+    /// When searching for the first item in an array matching a condition, it may be tempting to use code like `arr.filter(x => x > 0)[0]`.
+    /// However, it is simpler to use `Array.prototype.find()` instead, `arr.find(x => x > 0)`, which also returns the first entry matching a condition.
+    /// Because the `.find()` only needs to execute the callback until it finds a match, it's also more efficient.
+    ///
+    /// ## Examples
+    ///
+    /// ### Invalid
+    ///
+    /// ```ts,expect_diagnostic,file=invalid.ts
+    /// [1, 2, 3].filter(x => x > 1)[0];
+    /// ```
+    ///
+    /// ```ts,expect_diagnostic,file=invalid2.ts
+    /// [1, 2, 3].filter(x => x > 1).at(0);
+    /// ```
+    ///
+    /// ### Valid
+    ///
+    /// ```ts,file=valid.ts
+    /// [1, 2, 3].find(x => x > 1);
+    /// ```
+    ///
+    pub UseFind {
+        version: "next",
+        name: "useFind",
+        language: "js",
+        recommended: false,
+        sources: &[RuleSource::EslintTypeScript("prefer-find").same()],
+        domains: &[RuleDomain::Project],
+    }
+}
+
+fn is_first_position(ctx: &RuleContext<UseFind>, express: &AnyJsExpression) -> bool {
+    ctx.type_of_expression(express).is_number_literal(0.)
+        || ctx.type_of_expression(express).is_bigint_literal(0)
+}
+
+impl Rule for UseFind {
+    type Query = Typed<JsCallExpression>;
+    type State = TextRange;
+    type Signals = Option<Self::State>;
+    type Options = UseFindOptions;
+
+    fn run(ctx: &RuleContext<Self>) -> Self::Signals {
+        let binding = ctx.query();
+        let binding_callee = binding.callee().ok()?;
+        let binding_callee_static = binding_callee.as_js_static_member_expression()?;
+
+        let member = binding_callee_static.member().ok()?;
+        let member_name = member.as_js_name()?;
+        let member_value = member_name.value_token().ok()?;
+        if member_value.text_trimmed() != "filter" {
+            return None;
+        }
+
+        let parent = binding.syntax().parent()?;
+
+        // Handle .filter()[0]
+        if JsComputedMemberExpression::can_cast(parent.kind()) {
+            let express = JsComputedMemberExpression::cast(parent)?;
+            let member = express.member().ok()?;
+
+            if is_first_position(ctx, &member) {
+                return Some(express.range());
+            }
+
+        // Handle .filter().at(0)
+        } else if JsStaticMemberExpression::can_cast(parent.kind()) {
+            let express = JsStaticMemberExpression::cast(parent)?;
+
+            let member = express.member().ok()?;
+            let value_token = member.value_token().ok()?;
+            if value_token.text_trimmed() != "at" {
+                return None;
+            }
+
+            let call_parent = express.syntax().parent()?;
+            let call_parent_express = JsCallExpression::cast(call_parent)?;
+            let arguments = call_parent_express.arguments().ok()?;
+            let first_arg = arguments.args().first()?.ok()?;
+            let first_arg_express = first_arg.as_any_js_expression()?;
+
+            if is_first_position(ctx, first_arg_express) {
+                return Some(call_parent_express.range());
+            }
+        }
+
+        None
+    }
+
+    fn diagnostic(_ctx: &RuleContext<Self>, state: &Self::State) -> Option<RuleDiagnostic> {
+        Some(
+            RuleDiagnostic::new(
+                rule_category!(),
+                state,
+                markup! {
+                    "Prefer using Array#find() over Array#filter[0]."
+                },
+            )
+            .note(markup! {
+                "Use Array#find() instead of Array#filter[0] to improve readability."
+            }),
+        )
+    }
+}
diff --git a/crates/biome_js_analyze/tests/specs/nursery/useFind/invalid.ts b/crates/biome_js_analyze/tests/specs/nursery/useFind/invalid.ts
@@ -0,0 +1,8 @@
+[1, 2, 3].filter(x => x > 1)[0];
+const found1 = [1, 2, 3].filter(x => x > 1)[0];
+
+[1, 2, 3].filter(x => x > 1).at(0);
+const found2 = [1, 2, 3].filter(x => x > 1).at(0);
+
+[1, 2, 3].concat([56, 76, 4543]).filter(x => x > 1)[0].toString();
+[1, 2, 3].concat([56, 76, 4543]).filter(x => x > 1).at(0)?.toString();
diff --git a/crates/biome_js_analyze/tests/specs/nursery/useFind/invalid.ts.snap b/crates/biome_js_analyze/tests/specs/nursery/useFind/invalid.ts.snap
@@ -0,0 +1,113 @@
+---
+source: crates/biome_js_analyze/tests/spec_tests.rs
+expression: invalid.ts
+---
+# Input
+```ts
+[1, 2, 3].filter(x => x > 1)[0];
+const found1 = [1, 2, 3].filter(x => x > 1)[0];
+
+[1, 2, 3].filter(x => x > 1).at(0);
+const found2 = [1, 2, 3].filter(x => x > 1).at(0);
+
+[1, 2, 3].concat([56, 76, 4543]).filter(x => x > 1)[0].toString();
+[1, 2, 3].concat([56, 76, 4543]).filter(x => x > 1).at(0)?.toString();
+
+```
+
+# Diagnostics
+```
+invalid.ts:1:1 lint/nursery/useFind ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  i Prefer using Array#find() over Array#filter[0].
+
+  > 1 │ [1, 2, 3].filter(x => x > 1)[0];
+      │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    2 │ const found1 = [1, 2, 3].filter(x => x > 1)[0];
+    3 │ 
+
+  i Use Array#find() instead of Array#filter[0] to improve readability.
+
+
+```
+
+```
+invalid.ts:2:16 lint/nursery/useFind ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  i Prefer using Array#find() over Array#filter[0].
+
+    1 │ [1, 2, 3].filter(x => x > 1)[0];
+  > 2 │ const found1 = [1, 2, 3].filter(x => x > 1)[0];
+      │                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    3 │ 
+    4 │ [1, 2, 3].filter(x => x > 1).at(0);
+
+  i Use Array#find() instead of Array#filter[0] to improve readability.
+
+
+```
+
+```
+invalid.ts:4:1 lint/nursery/useFind ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  i Prefer using Array#find() over Array#filter[0].
+
+    2 │ const found1 = [1, 2, 3].filter(x => x > 1)[0];
+    3 │ 
+  > 4 │ [1, 2, 3].filter(x => x > 1).at(0);
+      │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    5 │ const found2 = [1, 2, 3].filter(x => x > 1).at(0);
+    6 │ 
+
+  i Use Array#find() instead of Array#filter[0] to improve readability.
+
+
+```
+
+```
+invalid.ts:5:16 lint/nursery/useFind ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  i Prefer using Array#find() over Array#filter[0].
+
+    4 │ [1, 2, 3].filter(x => x > 1).at(0);
+  > 5 │ const found2 = [1, 2, 3].filter(x => x > 1).at(0);
+      │                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    6 │ 
+    7 │ [1, 2, 3].concat([56, 76, 4543]).filter(x => x > 1)[0].toString();
+
+  i Use Array#find() instead of Array#filter[0] to improve readability.
+
+
+```
+
+```
+invalid.ts:7:1 lint/nursery/useFind ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  i Prefer using Array#find() over Array#filter[0].
+
+    5 │ const found2 = [1, 2, 3].filter(x => x > 1).at(0);
+    6 │ 
+  > 7 │ [1, 2, 3].concat([56, 76, 4543]).filter(x => x > 1)[0].toString();
+      │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    8 │ [1, 2, 3].concat([56, 76, 4543]).filter(x => x > 1).at(0)?.toString();
+    9 │ 
+
+  i Use Array#find() instead of Array#filter[0] to improve readability.
+
+
+```
+
+```
+invalid.ts:8:1 lint/nursery/useFind ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  i Prefer using Array#find() over Array#filter[0].
+
+    7 │ [1, 2, 3].concat([56, 76, 4543]).filter(x => x > 1)[0].toString();
+  > 8 │ [1, 2, 3].concat([56, 76, 4543]).filter(x => x > 1).at(0)?.toString();
+      │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    9 │ 
+
+  i Use Array#find() instead of Array#filter[0] to improve readability.
+
+
+```
diff --git a/crates/biome_js_analyze/tests/specs/nursery/useFind/valid.ts b/crates/biome_js_analyze/tests/specs/nursery/useFind/valid.ts
@@ -0,0 +1,13 @@
+/* should not generate diagnostics */
+[1, 2, 3].find(x => x > 1);
+[1, 2, 3].filter(x => x > 1)[1];
+const foundArray = [1, 2, 3].filter(x => x > 1)[1];
+
+[1, 2, 3].filter(x => x > 1).concat([5, 6, 7])[0];
+
+const obj = {
+	find: () => {
+		return [1, 2, 3]
+	}
+}
+obj.find()[0];
diff --git a/crates/biome_js_analyze/tests/specs/nursery/useFind/valid.ts.snap b/crates/biome_js_analyze/tests/specs/nursery/useFind/valid.ts.snap
@@ -0,0 +1,21 @@
+---
+source: crates/biome_js_analyze/tests/spec_tests.rs
+expression: valid.ts
+---
+# Input
+```ts
+/* should not generate diagnostics */
+[1, 2, 3].find(x => x > 1);
+[1, 2, 3].filter(x => x > 1)[1];
+const foundArray = [1, 2, 3].filter(x => x > 1)[1];
+
+[1, 2, 3].filter(x => x > 1).concat([5, 6, 7])[0];
+
+const obj = {
+	find: () => {
+		return [1, 2, 3]
+	}
+}
+obj.find()[0];
+
+```
diff --git a/crates/biome_js_type_info/src/type.rs b/crates/biome_js_type_info/src/type.rs
@@ -200,6 +200,21 @@ impl Type {
         })
     }
 
+    /// Returns whether this type is a bigint with the given `value`.
+    pub fn is_bigint_literal(&self, value: i64) -> bool {
+        self.as_raw_data().is_some_and(|ty| match ty {
+            TypeData::Literal(literal) => match literal.as_ref() {
+                Literal::BigInt(literal) => literal
+                    .trim_end_matches('n')
+                    .parse::<i64>()
+                    .ok()
+                    .is_some_and(|literal_value| literal_value == value),
+                _ => false,
+            },
+            _ => false,
+        })
+    }
+
     /// Returns whether this type is the `Promise` class.
     pub fn is_promise(&self) -> bool {
         self.id == GLOBAL_PROMISE_ID

diff --git a/crates/biome_rule_options/src/lib.rs b/crates/biome_rule_options/src/lib.rs
@@ -292,6 +292,7 @@ pub mod use_exponentiation_operator;
 pub mod use_export_type;
 pub mod use_exports_last;
 pub mod use_filenaming_convention;
+pub mod use_find;
 pub mod use_flat_map;
 pub mod use_focusable_interactive;
 pub mod use_for_of;

diff --git a/crates/biome_rule_options/src/use_find.rs b/crates/biome_rule_options/src/use_find.rs
@@ -0,0 +1,6 @@
+use biome_deserialize_macros::{Deserializable, Merge};
+use serde::{Deserialize, Serialize};
+#[derive(Default, Clone, Debug, Deserialize, Deserializable, Merge, Eq, PartialEq, Serialize)]
+#[cfg_attr(feature = "schema", derive(schemars::JsonSchema))]
+#[serde(rename_all = "camelCase", deny_unknown_fields, default)]
+pub struct UseFindOptions {}