JavaScript

Array iteration in JavaScript means looping through each item in an array and performing actions like displaying data, modifying values, or filtering elements.

JavaScript offers several powerful methods for iterating over arrays.

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✅ 1. for Loop – Traditional Way

The classic for loop gives full control over the iteration process.

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

for (let i = 0; i < fruits.length; i++) {
  console.log(fruits[i]);
}

🔹 Best when you need access to the index or want to break/continue early.

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✅ 2. forEach() – Easy and Clean

forEach() executes a function once for each array item.

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

colors.forEach(function(color) {
  console.log(color);
});

Or with arrow function:

colors.forEach(color => console.log(color));

🔹 You can’t use break or return to exit early in forEach().

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✅ 3. for...of Loop – Simple and Readable

for...of iterates over array values directly.

let scores = [80, 90, 70];

for (let score of scores) {
  console.log(score);
}

🔹 Cleaner than for, and supports break and continue.

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✅ 4. map() – Create a New Array

map() creates a new array by applying a function to each element.

let numbers = [1, 2, 3];

let doubled = numbers.map(num => num * 2);
console.log(doubled); // [2, 4, 6]

🔹 Perfect when you need to transform array data.

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✅ 5. filter() – Filter Values

Returns a new array containing only the matching elements.

let ages = [15, 22, 18, 30];

let adults = ages.filter(age => age >= 18);
console.log(adults); // [22, 18, 30]

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✅ 6. reduce() – Reduce to a Single Value

Reduces the array to a single result (like sum or average).

let prices = [10, 20, 30];

let total = prices.reduce((sum, price) => sum + price, 0);
console.log(total); // 60

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✅ 7. every() & some() – Test Conditions

• every() returns true if all elements pass the test.
• some() returns true if any element passes the test.

let numbers = [2, 4, 6];

console.log(numbers.every(n => n % 2 === 0)); // true
console.log(numbers.some(n => n > 5)); // true

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📌 Summary Table

Method	Description	Returns
for	Traditional loop with full control	–
forEach()	Calls a function for each item	undefined
for...of	Iterates over array values	–
map()	Transforms array, returns new array	New array
filter()	Filters values, returns matching ones	New array
reduce()	Reduces to a single value	Any value
every()	Checks if all elements pass a test	true/false
some()	Checks if any element passes a test	true/false

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🧠 Final Thoughts

• Use for or for...of when you need control over the loop.
• Use forEach() for clean, simple iteration.
• Use map(), filter(), reduce() for functional programming.
• Use every() and some() to test conditions.

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