Storing Lists of Data

If you need to store 100 usernames, you wouldn't create 100 different variables. Instead, you use an Array. An array is a special variable that can hold more than one value at a time.

let frameworks = ["React", "Next.js", "Vue"];
console.log(frameworks[0]); // Outputs: "React" (Arrays are zero-indexed!)

Essential Array Methods

Arrays come with built-in methods that make managing lists incredibly easy.

1. push() and pop()

push() adds a new item to the end of the array.
pop() removes the last item from the end of the array.

let stack = ["HTML", "CSS"];
stack.push("JavaScript"); // ["HTML", "CSS", "JavaScript"]
stack.pop(); // Removes "JavaScript"

2. unshift() and shift()

unshift() adds a new item to the beginning of the array.
shift() removes the first item from the beginning of the array.

3. length Just like strings, you can find the size of an array:

console.log(stack.length);

4. join() Converts an array into a string, separated by whatever character you choose.

let names = ["Himanshu", "Dubey"];
console.log(names.join(" ")); // "Himanshu Dubey"

💡 Himanshu's Tip:

When you use const to declare an array, you can still push() or pop() items! const only prevents you from completely reassigning the variable to a brand new array. Always declare your arrays with const.

Interview Questions

How do you access the last element of an array if you don't know its exact length?
What is the difference between push() and unshift(), and which one is faster in terms of performance?
Can a single JavaScript array hold mixed data types (e.g., Numbers and Strings together)?