JavaScript

The following are useful references. You can go through it to refresh your JavaScript knowledge.

• JavaScript Notes & Reference: To find all in one place about JavaScript you can explore this.
• ES6 Tutorial: ES6 tutorials and guidelines.
• ECMAScript History: Various versions of ECMAScript.
• Clean Code concepts adapted for JavaScript: To learn and practice clean coding concept of JavaScript, please follow this link.
• ESNext: A comprehensive list of all additions to ECMAScript after ES6.

Try it out!

1. Fix the following code snippet that attempts to calculate the sum of an array.

/**
 * Calculates the sum of all elements in an array.
 * 
 * @param {number[]} arr - The array of numbers to sum.
 * @returns {number} The sum of the elements in the array.
 */
function sumArray(arr) {
  let sum = 0;
  for (let i = 0; i <= arr.length; i++) {
    sum += arr[i];
  }
  return sum;
}

console.log(sumArray([1, 2, 3, 4])); // Expected output: 10

2. What will be the output of the following and why?

let a = 3;
let b = "3";

console.log( a+b );
console.log( b+a);

console.log( b*a );
console.log( a*b );

console.log( a/b );
console.log( b/a );

console.log( a-b );
console.log( b-a );

Ideas to Explore:

• What are closures in JavaScript?
• What is the event loop in JavaScript?
• What is the difference between null and undefined in JavaScript?
• What are pseudo-classes and pseudo-elements in CSS? Read about different ones of those.