JavaScript Array Methods Every Beginner Should Know

When learning JavaScript, arrays show up everywhere.
And instead of writing long loops every time, JavaScript gives us built-in array methods that make things easier.

Let’s go through some of the most common ones.

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push() and pop()

These work on the end of an array.

push()

Adds an item to the end.

Before:

let nums = [1, 2, 3]

nums.push(4)

After:

[1, 2, 3, 4]

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pop()

Removes the last item.

Before:

[1, 2, 3, 4]

nums.pop()

After:

[1, 2, 3]

Simple stack-like behavior.

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shift() and unshift()

These work on the start of the array.

shift()

Removes the first element.

Before:

let nums = [1, 2, 3]

nums.shift()

After:

[2, 3]

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unshift()

Adds element at the beginning.

nums.unshift(0)

After:

[0, 2, 3]

These are useful but slightly slower because array positions shift.

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forEach()

forEach() runs a function for every item in the array.

Example:

let nums = [1,2,3]

nums.forEach(num => {
  console.log(num)
})

Output:

1
2
3

It’s mainly used when you just want to do something with each item, not create a new array.

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map()

map() creates a new array by transforming each element.

Example:

let nums = [1,2,3]

let doubled = nums.map(n => n * 2)

Result:

[2,4,6]

Original array stays the same.

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Traditional loop vs map()

Traditional loop:

let result = []

for(let i=0;i<nums.length;i++){
  result.push(nums[i]*2)
}

With map():

let result = nums.map(n => n*2)

Much cleaner.

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filter()

filter() creates a new array containing only items that match a condition.

Example:

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

let big = nums.filter(n => n > 10)

Result:

[15,20]

So filter basically removes elements that don’t pass the test.

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reduce() (basic idea)

reduce() is used to combine all values into a single result.

Example: sum of numbers

let nums = [1,2,3,4]

let total = nums.reduce((sum,n) => sum + n, 0)

Result:

10

Here:

• sum keeps accumulating

• each number gets added

Reduce can do many things, but beginners mostly use it for totals.

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Small practice idea

Try this in your browser console.

let nums = [5,8,12,20]

Double each number:

nums.map(n => n*2)

Get numbers greater than 10:

nums.filter(n => n>10)

Find total sum:

nums.reduce((sum,n)=>sum+n,0)

Just experimenting with these a few times makes them stick.

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Final thought

You can still use for loops, but methods like map, filter, and reduce make code shorter and easier to read.

Once you get comfortable with them, working with arrays becomes much smoother.