#80 Find maximum number of 1s in JavaScript array

To find the maximum number of 1s in a JavaScript array, we can interpret this question in two main ways:

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🔹 Case 1: Count total number of 1s

Count all the 1s in the array (regardless of their position).

✅ Approach 1: Using filter()

const arr = [1, 0, 1, 1, 0, 1];
const count = arr.filter(x => x === 1).length;
console.log(count); // Output: 4

• ✅ Simple and readable.
• ❌ Creates a temporary array in memory.

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✅ Approach 2: Using reduce()

const arr = [1, 0, 1, 1, 0, 1];
const count = arr.reduce((acc, curr) => acc + (curr === 1 ? 1 : 0), 0);
console.log(count); // Output: 4

• ✅ Memory efficient.
• ✅ Flexible for conditions.

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✅ Approach 3: Using for loop

const arr = [1, 0, 1, 1, 0, 1];
let count = 0;

for (let i = 0; i < arr.length; i++) {
  if (arr[i] === 1) count++;
}
console.log(count); // Output: 4

• ✅ Fastest.
• ✅ No extra memory.
• ✅ Good for large arrays.

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🔹 Case 2: Find maximum number of consecutive 1s

Count the longest sequence of continuous 1s.

✅ Approach 1: Using for loop

const arr = [1, 1, 0, 1, 1, 1, 0, 1];
let max = 0, current = 0;

for (let i = 0; i < arr.length; i++) {
  if (arr[i] === 1) {
    current++;
    max = Math.max(max, current);
  } else {
    current = 0;
  }
}

console.log("Max consecutive 1s:", max); // Output: 3

• ✅ Best approach for consecutive 1s.
• ✅ Handles mixed arrays easily.

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🟢 Summary:

Goal	Method	Description
Count total 1s	filter(), reduce(), or for loop	Straightforward count
Max consecutive 1s	for loop with counters	Track streaks of 1s