𝗝𝗮𝘃𝗮𝗦𝗰𝗿𝗶𝗽𝘁 𝗪𝗲𝗲𝗸 𝟭 𝗠𝗼𝗰𝗸 𝗤𝘂𝗲𝘀𝘁𝗶𝗼𝗻𝘀

𝗝𝗮𝘃𝗮𝗦𝗰𝗿𝗶𝗽𝘁 𝗪𝗲𝗲𝗸 𝟭 𝗠𝗼𝗰𝗸 𝗤𝘂𝗲𝘀𝘁𝗶𝗼𝗻𝘀

Prepare for your JavaScript interviews. Here are key concepts you need to know.

CSS Hiding

• display none removes the element. It takes no space.
• visibility hidden hides the element. It keeps its space.

CSS Units

• px is a fixed size.
• % is relative to the parent.
• em is relative to the parent font size.
• rem is relative to the root font size.

Optional Chaining

• Use ?. to read nested properties.
• It stops your app from crashing.
• It returns undefined if the property is missing.

Bitwise Operators

• These work on binary numbers.
• Use & for AND.
• Use | for OR.
• Use ^ for XOR.
• Use ~ for NOT.

Type Casting

• Implicit conversion happens automatically.
• Explicit conversion happens when you use functions like Number().

Truthy and Falsy

• JavaScript has 8 falsy values.
• These are false, 0, empty strings, null, undefined, and NaN.
• Everything else is truthy.

Variable Declarations

• var is function scoped.
• let is block scoped.
• const is block scoped. Its value stays the same.

Mutable and Immutable

• Mutable objects change after creation. Examples are Arrays and Objects.
• Immutable values stay the same. Examples are Strings and Numbers.

Source: https://dev.to/dev_saravanan_journey/javascript-week-1-mock-questions-with-answers-3l9g