Javascript

Question 1

What are 7 built-in types in JavaScript (ES6)?

Answer 1

null, undefined, boolean, number, string, object, and symbol.

All are primitives except for object

Question 2

Null vs. Undefined?

Answer 2

Undefined is the absence of a definition. It is used as the default value for uninitialized variables, function arguments that were not provided and missing properties of objects.
- Functions return undefined when nothing has been explicitly returned.

Null is the absence of a value. It is an assignment value that can be assigned to a variable as a representation of ‘no-value’.

Question 3

Implicit Coercion. Boolean coercion. What is falsy and what is truthy?

Answer 3

Falsy values: “”, 0, null, undefined, NaN, false.

Truthy: everything else. Empty arrays, objects, and functions are coerced to true.

Question 4

String & Number coercion. What can you tell me?

Answer 4

The + operator works for both strings and numbers.
The *, /, and - operators are exclusive for numeric operations. When strings use these, they will be coerced to a number.

If a + is used with strings and numbers, they will be coerced into a string.

Question 5

== vs. ===

Answer 5

== checks for equality with coercion. 
=== checks for equality without coercion. strict equality.