JavaScriptEasy
What is the difference between var, let and const in JavaScript?
var is function-scoped and can be redeclared; let and const are block-scoped, and const cannot be reassigned after it is set.
Intern 路 Junior 路 Functions & Scope
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169 questions
- JavaScriptEasy
What is the difference between == and === in JavaScript?
== compares values after type coercion, while === compares both value and type with no conversion, so it is the safer default.
Intern 路 Junior 路 Programming Fundamentals - JavaScriptEasy
What is hoisting in JavaScript?
Hoisting is JavaScript moving declarations to the top of their scope during compilation, so functions and var variables can be referenced before the line where they are written.
Intern 路 Junior 路 Functions & Scope - JavaScriptEasy
What is the difference between null and undefined in JavaScript?
undefined means a variable has been declared but no value was assigned; null is an explicit value meaning 'no value' that you assign on purpose.
Intern 路 Junior 路 Programming Fundamentals - JavaScriptEasy
What is the difference between map, filter and reduce in JavaScript?
map transforms every item into a new array of the same length, filter keeps only items that pass a test, and reduce folds the whole array into a single value.
Intern 路 Junior 路 Functions & Scope - ReactEasy
What is the virtual DOM in React and how does it work?
The virtual DOM is a lightweight JavaScript copy of the UI that React compares with the previous version after each update, so it only changes the parts of the real DOM that actually differ.
Intern 路 Junior 路 Performance - ReactEasy
What is the difference between props and state in React?
Props are read-only inputs passed from a parent component, while state is data a component owns and can change over time, which triggers a re-render when updated.
Intern 路 Junior 路 State Management - HTMLEasy
What are semantic HTML elements and why do they matter?
Semantic elements describe their meaning in the name, such as header, nav, main, article and footer, so browsers, assistive technology and search engines can understand the page structure.
Intern 路 Junior 路 Accessibility - CSSEasy
What is the CSS box model?
Every element is a box made of content, padding, border and margin. The default content-box size counts only the content; border-box includes padding and border in the width you set.
Intern 路 Junior 路 CSS Layout - CSSEasy
What is the difference between display none and visibility hidden in CSS?
display: none removes the element from the layout so it takes no space; visibility: hidden hides it but leaves the empty space, and the element can still be read in the accessibility tree in some cases.
Intern 路 Junior 路 CSS Layout - CSSEasy
What is the difference between inline, block and inline-block in CSS?
Block elements start on a new line and take the full available width; inline elements sit in the text flow and ignore width and height; inline-block sits in the flow but accepts width, height, padding and margin on all sides.
Intern 路 Junior 路 CSS Layout - TypeScriptEasy
What is TypeScript and why do we use it?
TypeScript is a typed superset of JavaScript that compiles to plain JavaScript. It catches type errors in the editor and at build time, and it documents the shape of data for the next person who reads the code.
Intern 路 Junior 路 Types & Type System - TypeScriptEasy
What is the difference between interface and type in TypeScript?
Both describe object shapes. interface can be merged and is preferred for public object contracts; type can express unions, intersections and primitives, and cannot be reopened later.
Intern 路 Junior 路 Types & Type System - Node.jsEasy
What is Node.js and why is it called single-threaded?
Node.js is a JavaScript runtime built on Chrome's V8 engine that runs your JavaScript on a single main thread and uses non-blocking I/O, so one thread can handle many concurrent connections.
Intern 路 Junior 路 Asynchronous Programming - Node.jsEasy
What is the difference between package.json and package-lock.json?
package.json lists your project's dependencies with allowed version ranges, while package-lock.json records the exact versions that were installed so every machine gets an identical dependency tree.
Intern 路 Junior 路 Programming Fundamentals - SQLEasy
What is the difference between INNER JOIN and LEFT JOIN in SQL?
INNER JOIN returns only rows that have a match in both tables, while LEFT JOIN returns every row from the left table and fills the right table's columns with NULL when there is no match.
Intern 路 Junior 路 SQL - SQLEasy
What is the difference between WHERE and HAVING in SQL?
WHERE filters individual rows before grouping, while HAVING filters groups after GROUP BY, so only HAVING can use aggregate functions like COUNT or SUM.
Intern 路 Junior 路 SQL - SQLEasy
What is the difference between DELETE, TRUNCATE and DROP in SQL?
DELETE removes selected rows and can be rolled back, TRUNCATE quickly removes all rows and keeps the table structure, and DROP removes the entire table including its structure.
Intern 路 Junior 路 SQL - SQLEasy
What is the difference between a primary key and a foreign key?
A primary key uniquely identifies each row in its own table and cannot be NULL, while a foreign key is a column that references the primary key of another table to link the two.
Intern 路 Junior 路 Database - C#Easy
What is the difference between a value type and a reference type in C#?
A value type variable holds its data directly and is copied on assignment, while a reference type variable holds a reference to an object, so assignment copies the reference and both variables see the same object.
Intern 路 Junior 路 Programming Fundamentals