arrayIndex.js

amit265 · amit265 · commit e7459fd94e36 · 2026-02-20T14:22:06.000+05:30
diff --git a/javascript/4_array-programs/arrayIndex.js b/javascript/4_array-programs/arrayIndex.js
@@ -0,0 +1,49 @@
+// 30. Find the Array Index with a Value
+
+// Using indexOf() - Most Used
+
+{
+  const a = [10, 20, 30, 40, 50];
+
+  const index = a.indexOf(30);
+
+  console.log(index);
+
+  // Value not found
+  const notFound = a.indexOf(60);
+  console.log(notFound);
+}
+
+// Using findIndex() for Complex Conditions
+
+{
+  const a = [10, 15, 20, 30, 40, 50];
+  // find index of first value greater than 18
+
+  const index = a.findIndex((value) => value > 18);
+  console.log(index);
+}
+
+// Using for Loop for Custom Search
+
+{
+  const a = [5, 10, 15, 20, 25];
+  let index = -1;
+  // find index of value 20
+
+  for (let i = 0; i < a.length; i++) {
+    if (a[i] === 25) {
+      index = i;
+      break;
+    }
+  }
+  console.log(index);
+}
+
+// Using lastIndexOf() for Reverse Search
+
+{
+  const a = [5, 10, 15, 1, 5];
+  const index = a.lastIndexOf(10);
+  console.log(index);
+}
