17 Questions
How do you create a new array with 10 boxes without any elements inside?
Declaring an array without assigning any values
What is the default separator used in the array.join() method?
Comma
What is the return value of the array.pop() method?
The removed element
What is the purpose of the array.length property?
To get the size of the array
How do you add a new element to the end of an array?
Using array.push()
What is the purpose of the array.concat() method?
To combine two arrays into one
What is the index of the first box in an array?
0
What is the purpose of short-circuit in AND operation in JavaScript?
To optimize the evaluation process by skipping unnecessary checks
What is the result of an OR operation if both inputs are false?
False
What is an array in JavaScript?
A linear continuous storage of data
What is the purpose of the NOT operator in JavaScript?
To negate the result of a boolean operation
What is the significance of the underscore character in JavaScript identifiers?
It can be used as the first character of a variable name
What is the data type of the variable 'big_number' in the following code: var big_number = 123e5;
Number
What is the difference between the variables 'myBool' and 'myString' in the following code?
myBool is a Boolean and myString is a String
What is the purpose of the curly braces in the following code: var person = { firstName:"John", lastName:"Doe", age:50, eyeColor:"blue" };
To define an object
What happens to the variable 'carName' in the following code: var carName = "Volvo"; var carName;
The variable 'carName' retains its original value
What is the significance of JavaScript being dynamically typed?
It means that variables can change data type during execution
Study Notes
Logical Operators
-
&&operator: returns true if both inputs are true, otherwise false - Short-Circuit in
&&: JavaScript stops checking if the first input is false -
||operator: returns false if both inputs are false, otherwise true - Short-Circuit in
||: JavaScript stops checking if the first input is true -
!operator: returns the opposite of the input
Arrays
- An array is a linear, continuous storage of data
- Each element in an array has a unique index, starting from 0
- Arrays can be thought of as a group of boxes
- How to create an array:
var myArray = [element1, element2, element3];
JavaScript Identifiers
- All JavaScript variables must have unique names (identifiers)
- Identifiers can be short names (like x, y) or more descriptive names (age, sum, totalVolume)
- Rules for constructing names:
- Can contain letters, digits, underscores, and dollar signs
- Must begin with a letter,
$, or_ - Case-sensitive (y and Y are different variables)
- Cannot use reserved words (like JavaScript keywords)
JavaScript Data Types
- Number: can be written with or without decimals, and can use scientific notation
- String: a sequence of characters, can use single or double quotes
- Boolean: can only be true or false
- Object: can be written with curly braces, and have properties as name:value pairs
- Function: a block of code that can be executed
- Null and undefined: cannot contain values
Working with Arrays
-
array.join(separator): converts an array into a string, with a separator (default is ",") - Retrieving an element from an array:
array[index] - Changing an element in an array:
array[index] = new_value -
array.length: returns the size of an array (number of elements) -
array.push(element): adds a new element to the end of an array -
array.unshift(element): adds a new element to the front of an array -
array.pop(): removes an element from the end of an array and returns it -
array.shift(): removes an element from the front of an array and returns it -
array1.concat(array2): combines two arrays into one
Generating Random Numbers
-
Math.random(): generates a random number between 0 and 1 - Setting up the range: multiply the result by a number to get the desired range
Test your understanding of JavaScript's logical operators AND (&&) and OR (||), including their short-circuit behavior. Learn how JavaScript evaluates these operators and how they can be used effectively in your code.
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