Sometimes in JavaScript, we need to find not just the largest number in an array, but also:

👉 How many times the largest number appears

In this post, you’ll learn:

• How to find the largest number
• How to count its occurrences
• Two approaches: filter() and reduce()
• Step-by-step explanation

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Problem Statement

Given an array:

const sampleArray = [5, 5, 2, 4, 5];

👉 Output should be:

Count of largest numbers in the array: 3

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Step 1: Find the Largest Number

We use Math.max():

const largestNumber = Math.max(...sampleArray);

👉 Result:

largestNumber = 5

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Method 1: Using filter() (Simple & Readable)

const sampleArray = [5, 5, 2, 4, 5];

const largestNumber = Math.max(...sampleArray);

const count = sampleArray.filter(num => num === largestNumber).length;

console.log("Count of largest numbers:", count); // 3

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How It Works

• filter() checks each element
• Keeps only values equal to largestNumber
• .length gives the count

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Execution Flow

Array:

[5, 5, 2, 4, 5]

Filtered:

[5, 5, 5]

Count:

3

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Method 2: Using reduce() (Interview Favorite)

const sampleArray = [5, 5, 2, 4, 5];

const largestNumber = Math.max(...sampleArray);

const count = sampleArray.reduce((acc, curr) => {
  return acc + (curr === largestNumber ? 1 : 0);
}, 0);

console.log("Count of largest numbers:", count); // 3

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How reduce() Works

• acc → accumulator (count)
• curr → current element

👉 If value equals largest number → add 1
👉 Otherwise → add 0

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Step-by-Step Execution

Step	curr	Condition	acc
Start	–	–	0
1	5	true	1
2	5	true	2
3	2	false	2
4	4	false	2
5	5	true	3

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Edge Cases

1. Empty Array

const arr = [];

👉 Math.max(...arr) returns -Infinity

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2. All Same Values

[3, 3, 3]

👉 Count = 3

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filter() vs reduce()

Feature	filter()	reduce()
Readability	Easy	Moderate
Performance	Slightly more memory	Better
Interview	Less preferred	Highly preferred

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Interview Tip

If asked:

“How to count occurrences of max number?”

Answer:

“First find the max using Math.max, then use filter or reduce to count occurrences.”

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Real-World Use Cases

• Finding top scores
• Sales analysis
• Data analytics
• Ranking systems

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Related Articles

👉 You can also check:

• How to Find Sum of Array Using reduce() in JavaScript (Step-by-Step Execution Explained)
• TypeError: Reduce of Empty Array with No Initial Value (Fix Explained)

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Final Summary

• Use Math.max() to find largest number
• Use filter() for simplicity
• Use reduce() for better control
• Always handle edge cases

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