Javascript Code Snippets For Interview
Top 10
Javascript code snippets are short, self-contained pieces of code that can be reused and inserted into a larger program. They are commonly used during interviews to showcase a candidate's coding skills and problem-solving abilities. These snippets cover a variety of concepts and can range from simple to complex, allowing interviewers to assess a candidate's understanding of Javascript syntax, logic, and functionality. Additionally, code snippets can also help to save time during an interview by providing a structured and ready-made solution for a specific problem, allowing the candidate to focus on explaining their thought process and approach.
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1 - Explain what is JavaScript and its basic features:
JavaScript is a scripting language used for creating interactive and dynamic web pages.
It is a client side language, which means it runs on the user's browser, making it lightweight and fast.
JavaScript can be integrated with HTML and CSS to create visually appealing and responsive web pages.
It has a syntax similar to C language and is a high level programming language.
JavaScript supports object oriented, functional, and imperative programming styles.
It has a rich set of built in methods and functions, making it flexible for various programming needs.
Additionally, it supports third party libraries and frameworks such as React, Angular, and jQuery.
2) How to declare a variable in JavaScript:
To declare a variable in JavaScript, we use the ‘var’, ‘let’, or ‘const’ keyword, followed by the variable name and optionally an assigned value.
For example, var myVariable = 10;
The ‘var’ keyword is used to declare a variable globally or locally within a function, but its scope can be changed.
The ‘let’ keyword is used to declare a block scoped variable, meaning it can only be accessed within the nearest curly braces.
The ‘const’ keyword is used to declare a variable with a constant value that cannot be reassigned.
3) What are the different data types in JavaScript:
The primitive data types in JavaScript are string, number, boolean, null, undefined, and symbol (introduced in ES6).
Non primitive data types include objects (arrays, functions, objects, and dates) and the special type ‘object’.
4) What is the difference between == and === in JavaScript:
The ‘==’ operator checks for the value of the operands, while ‘===’ checks for both value and data type.
For example, 10 == ‘10’ will return true, but 10 === ‘10’ will return false.
5) What is a closure in JavaScript:
A closure is a function that has access to variables defined in its outer scope even after the outer function has returned.
This allows for data encapsulation and helps with memory management in JavaScript.
6) What are the different ways to define a function in JavaScript:
Functions can be defined using the ‘function’ keyword, arrow functions (introduced in ES6), and function expressions.
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ES6 also introduced the ‘class’ keyword for creating classes and constructors, which are essentially special types of functions in JavaScript.
7) How to use a for loop in JavaScript:
A for loop is used to iterate over a block of code a specific number of times.
It has three components: the initialization, condition, and final expression.
For example, for (let i = 0; i < 10; i++) { //code to be executed }
8) Explain what is hoisting in JavaScript:
Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their scope before the code is executed.
This allows variables and functions to be used before they are declared, but it is advisable to declare them first for better code readability.
9) How to check if a variable is an array in JavaScript:
To check if a variable is an array in JavaScript, we can use the Array.isArray() method.
For example, Array.isArray(myVariable) will return true if myVariable is an array and false if it is not.
10) What is event bubbling in JavaScript:
Event bubbling is the concept where an event is triggered on a child element and then propagates up through its parent elements.
This behavior can be stopped using the event.stopPropagation() method.
11) How to convert a string to an array in JavaScript:
We can use the split() method to convert a string to an array in JavaScript.
This method takes in a delimiter as an argument and splits the string at each occurrence of the delimiter.
For example, let myArray = myString.split(',') will split the string at each comma and store the values in an array.
12) How to use the ternary operator in JavaScript:
The ternary or conditional operator is a shorthand version of an if/else statement that evaluates a condition and returns a value based on the result.
It has the form of ‘condition ? trueValue : falseValue’.
For example, let result = (myVariable > 10) ? ‘greater than 10’ : ‘less than 10’;
13) How to loop through an object in JavaScript:
We can use the ‘for…in’ loop to iterate over the keys of an object and access their corresponding values.
For example, for (let key in myObject) { console.log(key + ‘: ’ + myObject[key]) }
14) Explain the difference between null and undefined in JavaScript:
In JavaScript, both null and undefined represent ‘no value’, but they have different meanings.
Null is explicitly set by a developer to indicate that a variable has no value, while undefined indicates that a variable has not been assigned a value or does not exist.
15) How to handle errors in JavaScript:
We can use the Keywords ‘try’, ‘catch’, and ‘finally’ to handle errors in JavaScript.
The ‘try’ block encloses the code that may throw an error, and if an error occurs, the ‘catch’ block is executed.
The ‘finally’ block is executed regardless of whether an error occurs or not, and it is used to perform cleanup and finalize code execution.
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