How to use the JavaScript compiler?
To use the Compiler, follow these steps:
- In the code editor, write your JavaScript code.
- Click the "RUN" button to compile and run your code.
- The output and error will be displayed in the editor.
Taking Inputs
String Input
This code snippet reads a string from the standard input (stdin) and prints it to the console.
function processInput(string1) {
console.log("You entered: " + string1);
}
// DO NOT EDIT ANY CODE BELOW THIS LINE
process.stdin.resume();
process.stdin.setEncoding('ascii');
var input_stdin = "";
var input_stdin_array = "";
var input_currentline = 0;
process.stdin.on('data', function (data) {
input_stdin += data;
});
process.stdin.on('end', function () {
input_stdin_array = input_stdin.split("\\n");
testCode();
});
function readLine() {
return input_stdin_array[input_currentline++].trim();
}
function testCode() {
var string1 = readLine();
processInput(string1.trim());
}
In this code, the processInput() function is used to process the input string and print it to the console. The readLine() function is used to read a line of input from the stdin, and the testCode() function is used to call the processInput() function with the input string.
Array of Numbers
This code snippet reads a line of numbers separated by commas from the stdin, converts it into an array of numbers, and prints the array to the console.
function processInput(numbers) {
console.log("Array of numbers: ", numbers);
}
// DO NOT EDIT ANY CODE BELOW THIS LINE
process.stdin.resume();
process.stdin.setEncoding('ascii');
var input_stdin = "";
var input_stdin_array = "";
var input_currentline = 0;
process.stdin.on('data', function (data) {
input_stdin += data;
});
process.stdin.on('end', function () {
input_stdin_array = input_stdin.split("\\n");
testCode();
});
function readLine() {
return input_stdin_array[input_currentline++].trim();
}
function testCode() {
var numbers = readLine().split(',').map(Number);
processInput(numbers);
}
In this code, the readLine() function reads a line of input from the stdin, and the split() and map() methods are used to convert the input string into an array of numbers. The processInput() function is then called with the array of numbers as an argument.
Matrix Input
This code snippet reads multiple lines of input from the stdin, each line containing numbers separated by commas, and converts them into a matrix (an array of arrays). The matrix is then printed to the console.
function processInput(matrix) {
console.log("Matrix: ", matrix);
}
// DO NOT EDIT ANY CODE BELOW THIS LINE
process.stdin.resume();
process.stdin.setEncoding('ascii');
var input_stdin = "";
var input_stdin_array = "";
var input_currentline = 0;
process.stdin.on('data', function (data) {
input_stdin += data;
});
process.stdin.on('end', function () {
input_stdin_array = input_stdin.split("\\n");
testCode();
});
function readLine() {
return input_stdin_array[input_currentline++].trim();
}
function testCode() {
var rows = readLine();
var matrix = [];
for(let i=0; i<rows; i++) {
let row = readLine().split(',').map(Number);
matrix.push(row);
}
processInput(matrix);
}
In this code, the readLine() function is used to read each line of input from the stdin. The first line of input is the number of
rows in the matrix. For each row, the readLine() function reads a line of input, and the split() and map() methods are used to convert the input string into an array of numbers. These arrays are then added to the matrix array. Finally, the processInput() function is called with the matrix as an argument.
JavaScript Online Test
A JavaScript online test is a powerful tool to evaluate an individual's JavaScript programming skills. These tests often include a variety of questions, ranging from multiple-choice theoretical questions to practical coding challenges. By solving these problems, candidates demonstrate their understanding of JavaScript concepts, problem-solving abilities, and coding proficiency. Such tests are commonly used in technical interviews, coding bootcamps, and online learning platforms to assess a learner's progress and proficiency in JavaScript.
JavaScript Syntax Basics
JavaScript is a dynamic, interpreted programming language that is primarily used for building web-based applications. Here's a primer on the major syntax basics of JavaScript:
Variables
Variables in JavaScript can be declared using var, let, or const.
var name = "John Doe"; // Old way of declaring variables, has function scope
let age = 25; // New way of declaring variables, has block scope
const pi = 3.14; // Declaring constants, cannot be reassigned
Data Types
JavaScript has several data types including Number, String, Boolean, Object, Null, and Undefined.
let num = 10; // Number
let str = "Hello World"; // String
let bool = true; // Boolean
let obj = {name: "John Doe", age: 25}; // Object
let n = null; // Null
let undef; // Undefined
Arrays
Arrays in JavaScript can hold multiple values and can be declared using square brackets [].
let arr = [1, 2, 3, 4, 5]; // Array of numbers
Control Structures
JavaScript includes control structures such as if, else, for, while, and switch.
// If-Else
if (age > 18) {
console.log("Adult");
} else {
console.log("Minor");
}
// For loop
for (let i = 0; i < 5; i++) {
console.log(i);
}
// While loop
let i = 0;
while (i < 5) {
console.log(i);
i++;
}
// Switch
switch (day) {
case "Monday":
console.log("Start of the work week");
break;
case "Friday":
console.log("End of the work week");
break;
default:
console.log("Midweek");
}
Functions
Functions in JavaScript can be declared using the function keyword.
function greet(name) {
console.log("Hello, " + name);
}
greet("John Doe"); // Calls the function with "John Doe" as the argument
Objects
Objects in JavaScript are collections of key-value pairs.
let person = {
name: "John Doe",
age: 25,
greet: function() {
console.log("Hello, " + this.name);
}
};
person.greet(); // Calls the greet method of the person object
Arrow Functions
Arrow functions provide a concise syntax to write functions in JavaScript. They are especially useful when working with function expressions, or higher-order functions.
const greet = (name) => {
console.log(`Hello, ${name}`);
}
greet("John Doe"); // Calls the function with "John Doe" as the argument
Promises
Promises in JavaScript represent a completion or failure of an asynchronous operation. They are used to handle asynchronous operations like server requests.
let promise = new Promise((resolve, reject) => {
let success = true;
if (success) {
resolve("The operation was a success!");
} else {
reject("The operation failed.");
}
});
promise.then((message) => {
console.log(message);
}).catch((message) => {
console.log(message);
});
Async/Await
The async and await keywords in JavaScript are used to work with promises in a more comfortable synchronous manner.
async function fetchData() {
try {
let response = await fetch('https://api.example.com/data');
let data = await response.json();
console.log(data);
} catch (error) {
console.log(error);
}
}
fetchData();
Modules
Modules in JavaScript are reusable pieces of code that can be exported from one program and imported for use in another program.
// lib.js
export function greet(name) {
console.log(`Hello, ${name}`);
}
// app.js
import { greet } from './lib.js';
greet("John Doe");
Template Literals
Template literals provide an easy way to interpolate variables and expressions into strings.
let name = "John Doe";
console.log(`Hello, ${name}`); // Outputs: Hello, John Doe
Destructuring Assignment
The destructuring assignment syntax in JavaScript makes it possible to unpack values from arrays, or properties from objects, into distinct variables.
let [a, b] = [1, 2];
console.log(a); // Outputs: 1
console.log(b); // Outputs: 2
let {name, age} = {name: "John Doe", age: 25};
console.log(name); // Outputs: John Doe
console.log(age); // Outputs: 25
These are some of the more advanced syntax elements of JavaScript. As you continue to explore JavaScript, you'll encounter even more concepts and features.
Functions
Functions in JavaScript are blocks of code designed to perform a particular task. A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses ().
function sayHello() {
console.log("Hello, world!");
}
sayHello(); // Calls the function
Functions can also take parameters, which are specified inside the parentheses at the time of function definition, and can be used inside the function.
function greet(name) {
console.log("Hello, " + name);
}
greet("John"); // Calls the function with "John" as the argument
Functions can also return values using the return statement.
function square(number) {
return number * number;
}
let result = square(5); // result is now 25
Object-Oriented Programming (OOP)
JavaScript supports the object-oriented programming (OOP) paradigm. In OOP, we organize our code using objects and classes.
An object is a collection of properties, and a property is an association between a name (or key) and a value. A property's value can be a function, in which case the property is known as a method.
let person = {
firstName: "John",
lastName: "Doe",
age: 25,
fullName: function() {
return this.firstName + " " + this.lastName;
}
};
console.log(person.fullName()); // Outputs: John Doe
A class is a type of function, but instead of using the keyword function to initiate it, we use the keyword class.
class Person {
constructor(firstName, lastName, age) {
this.firstName = firstName;
this.lastName = lastName;
this.age = age;
}
fullName() {
return this.firstName + " " + this.lastName;
}
}
let person = new Person("John", "Doe", 25);
console.log(person.fullName()); // Outputs: John Doe
In the class Person, constructor is a special method for creating and initializing an object created with a class. There can only be one special method with the name "constructor" in a class.
