JavaScript

In JavaScript, you can search through arrays to find values, check if an item exists, or get its position.

JavaScript provides multiple methods to help you search arrays easily and effectively.

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✅ 1. indexOf() – Find the First Index

The indexOf() method returns the index of the first occurrence of a value.

let fruits = ["Apple", "Banana", "Mango"];

console.log(fruits.indexOf("Banana")); // 1
console.log(fruits.indexOf("Orange")); // -1 (not found)

🔹 If the value is not found, it returns -1.

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✅ 2. lastIndexOf() – Find the Last Index

The lastIndexOf() method returns the last occurrence of a value.

let nums = [1, 2, 3, 2, 4, 2];
console.log(nums.lastIndexOf(2)); // 5

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✅ 3. includes() – Check if Value Exists

The includes() method checks whether a specific value is present in the array.

let colors = ["Red", "Green", "Blue"];

console.log(colors.includes("Green")); // true
console.log(colors.includes("Yellow")); // false

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✅ 4. find() – Find First Matching Element

The find() method returns the first item that satisfies a condition (callback function).

let ages = [14, 18, 21, 16];

let adult = ages.find(age => age >= 18);

console.log(adult); // 18

🔹 It returns undefined if no match is found.

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✅ 5. findIndex() – Find Index of First Match

Returns the index of the first element that satisfies a condition.

let nums = [5, 10, 15, 20];

let index = nums.findIndex(num => num > 10);
console.log(index); // 2

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✅ 6. filter() – Find All Matching Elements

Returns a new array containing all elements that match a condition.

let scores = [80, 45, 90, 70, 50];

let passed = scores.filter(score => score >= 60);
console.log(passed); // [80, 90, 70]

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📌 Quick Comparison Table

Method	Returns	Use Case
indexOf()	Index (first match)	Find position of a value
lastIndexOf()	Index (last match)	Find last occurrence
includes()	true / false	Check if value exists
find()	First matching value	Get value based on condition
findIndex()	Index of first match	Get index based on condition
filter()	Array of matching values	Get all values that match

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🧠 Summary

• Use indexOf() / lastIndexOf() for exact value searches.
• Use includes() for simple existence checks.
• Use find() and findIndex() when working with conditions.
• Use filter() to get all values that match a condition.

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