Podcast
Questions and Answers
In JavaScript, what is the primary role of the ECMAScript standard?
In JavaScript, what is the primary role of the ECMAScript standard?
- To maintain the original LiveScript specifications without incorporating modern updates.
- To introduce new JavaScript features that might cause fragmentation.
- To ensure interoperability and consistency across different JavaScript implementations. (correct)
- To promote `JScript` as the dominant scripting language in web development.
Which of the following practices best leverages external JavaScript files for web development?
Which of the following practices best leverages external JavaScript files for web development?
- Writing all JavaScript code directly within HTML files to reduce the number of files to manage.
- Using external .js files to promote reusability, better organization, and easier maintenance across multiple web pages. (correct)
- Including `<script>` tags within the .js file to ensure proper execution in the HTML document.
- Duplicating JavaScript code across multiple HTML files to avoid dependencies on external files.
When should including JavaScript in the <head> section of an HTML document be avoided?
When should including JavaScript in the <head> section of an HTML document be avoided?
- When the script's execution needs to occur before the page content is rendered.
- When the script can slow down page rendering, unless it's a small script. (correct)
- When using external JavaScript files linked with the `src` attribute.
- When the script is small and does not depend on the DOM.
Which of the following is the most accurate description of JavaScript statements?
Which of the following is the most accurate description of JavaScript statements?
What is the primary implication of JavaScript ignoring extra spaces, tabs, and line breaks?
What is the primary implication of JavaScript ignoring extra spaces, tabs, and line breaks?
How does the use of curly braces {} in JavaScript affect the execution of statements?
How does the use of curly braces {} in JavaScript affect the execution of statements?
What differentiates a JavaScript expression from a statement?
What differentiates a JavaScript expression from a statement?
What is the impact of JavaScript's case sensitivity on variable names?
What is the impact of JavaScript's case sensitivity on variable names?
How does JavaScript's handling of variable types compare to that of a strongly typed language?
How does JavaScript's handling of variable types compare to that of a strongly typed language?
How does the const declaration differ from let in JavaScript?
How does the const declaration differ from let in JavaScript?
What function does the typeof keyword serve in JavaScript?
What function does the typeof keyword serve in JavaScript?
How does JavaScript handle function invocation, and what is the role of the return statement?
How does JavaScript handle function invocation, and what is the role of the return statement?
What does it mean for Javascript to 'hoist' function declarations, and what are the implications for function expressions?
What does it mean for Javascript to 'hoist' function declarations, and what are the implications for function expressions?
How does JavaScript's lexical scoping influence variable accessibility within a script?
How does JavaScript's lexical scoping influence variable accessibility within a script?
What is a potential drawback of using global variables in JavaScript?
What is a potential drawback of using global variables in JavaScript?
What outcome can arise from using mixed data types in JavaScript?
What outcome can arise from using mixed data types in JavaScript?
What happens when parseInt() encounters a non-numeric character in a string?
What happens when parseInt() encounters a non-numeric character in a string?
When should you use the isNaN() function in JavaScript, and what does it determine?
When should you use the isNaN() function in JavaScript, and what does it determine?
How do === and !== differ from == and != in JavaScript comparisons, and why is this distinction important?
How do === and !== differ from == and != in JavaScript comparisons, and why is this distinction important?
In JavaScript, under what circumstances is the ternary operator most effectively utilized?
In JavaScript, under what circumstances is the ternary operator most effectively utilized?
JavaScript is exclusively a server-side scripting language.
JavaScript is exclusively a server-side scripting language.
In JavaScript, the innerText property is used to insert text into an HTML element with a specified ID.
In JavaScript, the innerText property is used to insert text into an HTML element with a specified ID.
JavaScript always requires semicolons to terminate statements, similar to Python.
JavaScript always requires semicolons to terminate statements, similar to Python.
In JavaScript, variable names are case-insensitive, meaning myVariable and myvariable are treated as the same variable.
In JavaScript, variable names are case-insensitive, meaning myVariable and myvariable are treated as the same variable.
In JavaScript, multiline comments are initiated with // and terminated with //.
In JavaScript, multiline comments are initiated with // and terminated with //.
Variables declared using let in JavaScript can not be reassigned new values after their initial assignment.
Variables declared using let in JavaScript can not be reassigned new values after their initial assignment.
A JavaScript function is executed automatically when it is defined, without needing to be invoked.
A JavaScript function is executed automatically when it is defined, without needing to be invoked.
In JavaScript, function declarations can be called before they are defined in the code due to a principle known as 'hoisting.'
In JavaScript, function declarations can be called before they are defined in the code due to a principle known as 'hoisting.'
In JavaScript, a local variable declared inside a function can be accessed and modified from outside the function.
In JavaScript, a local variable declared inside a function can be accessed and modified from outside the function.
JavaScript handles different data types the same way, regardless of whether they are strings or numbers.
JavaScript handles different data types the same way, regardless of whether they are strings or numbers.
The expression parseInt('42.5abc') in JavaScript, converts the string and returns 42.5.
The expression parseInt('42.5abc') in JavaScript, converts the string and returns 42.5.
The isNaN() function in JavaScript always returns false if the value being checked is a valid number.
The isNaN() function in JavaScript always returns false if the value being checked is a valid number.
In JavaScript, the string method used when converting from numbers to strings is convertToDecimal().
In JavaScript, the string method used when converting from numbers to strings is convertToDecimal().
In JavaScript, the modulus operator (%) can only be used with integer operands and not with floating-point numbers.
In JavaScript, the modulus operator (%) can only be used with integer operands and not with floating-point numbers.
The strict equality operator (===) in JavaScript performs type conversion before comparing two values.
The strict equality operator (===) in JavaScript performs type conversion before comparing two values.
The result of '42' + 8 in JavaScript does type conversion and numeric addition, producing the number 50.
The result of '42' + 8 in JavaScript does type conversion and numeric addition, producing the number 50.
In JavaScript, the ternary operator can only handle numerical values.
In JavaScript, the ternary operator can only handle numerical values.
The const keyword in JavaScript is used to declare variables that should not be re-initialized, while the let command declares a block-scoped local variable.
The const keyword in JavaScript is used to declare variables that should not be re-initialized, while the let command declares a block-scoped local variable.
The purpose of comments is to improve JavaScript code, even if they do not provide readability or debugging; comments automatically enhance code functionality.
The purpose of comments is to improve JavaScript code, even if they do not provide readability or debugging; comments automatically enhance code functionality.
In JavaScript, self-invoking functions are executed only when explicitly invoked, just like regular functions.
In JavaScript, self-invoking functions are executed only when explicitly invoked, just like regular functions.
Flashcards
What is JavaScript?
What is JavaScript?
A scripting language embedded in web browsers that enables client-side scripting.
What are JavaScript Language Basics?
What are JavaScript Language Basics?
Syntax, keywords, operators, and built-in objects in JavaScript.
What is Web Page Interaction?
What is Web Page Interaction?
Manipulating the DOM for dynamic content updates.
Web Applications
Web Applications
Signup and view all the flashcards
Inline JavaScript
Inline JavaScript
Signup and view all the flashcards
External JavaScript
External JavaScript
Signup and view all the flashcards
Writing to an HTML Element
Writing to an HTML Element
Signup and view all the flashcards
Alert Output
Alert Output
Signup and view all the flashcards
Console Output
Console Output
Signup and view all the flashcards
JavaScript Statements
JavaScript Statements
Signup and view all the flashcards
Keywords
Keywords
Signup and view all the flashcards
Operators
Operators
Signup and view all the flashcards
Whitespace
Whitespace
Signup and view all the flashcards
Variable Values
Variable Values
Signup and view all the flashcards
Expressions
Expressions
Signup and view all the flashcards
JavaScript Syntax
JavaScript Syntax
Signup and view all the flashcards
JavaScript function
JavaScript function
Signup and view all the flashcards
Function Hoisting
Function Hoisting
Signup and view all the flashcards
Scope
Scope
Signup and view all the flashcards
parseInt() and parseFloat()
parseInt() and parseFloat()
Signup and view all the flashcards
ECMAScript
ECMAScript
Signup and view all the flashcards
Using innerText
Using innerText
Signup and view all the flashcards
JavaScript Keywords
JavaScript Keywords
Signup and view all the flashcards
Braces{}
Braces{}
Signup and view all the flashcards
JavaScript Literals
JavaScript Literals
Signup and view all the flashcards
Declaring with var
Declaring with var
Signup and view all the flashcards
Declaring with const
Declaring with const
Signup and view all the flashcards
JavaScript Typing
JavaScript Typing
Signup and view all the flashcards
Function body
Function body
Signup and view all the flashcards
Function Return
Function Return
Signup and view all the flashcards
Local Scope
Local Scope
Signup and view all the flashcards
Arithmetic Operators
Arithmetic Operators
Signup and view all the flashcards
Assignment Operators
Assignment Operators
Signup and view all the flashcards
Ternary Operator
Ternary Operator
Signup and view all the flashcards
Study Notes
Basics of JavaScript
- An object-based scripting language that is embedded in web browsers like Chrome, Edge and Firefox
- Enables client-side scripting, which improves webpage responsiveness
- Brendan Eich created Javascript at Netscape in 1995.
- Initially named LiveScript
- Renamed JavaScript to align with Java's popularity
- The language itself is not related to Java
- Web pages relied on server-side scripts before JavaScript, causing slow response times
- Allows for faster, more interactive and dynamic web experiences within the browser
Standardization & Growth
- Microsoft introduced JScript, which led to concerns about fragmentation
- JavaScript was standardized as ECMAScript by Ecma International in 1997
- Most still refer to JavaScript by its original name
- Brendan Eich co-founded Mozilla and helped launch Firefox
Core Capabilities
- Language basics include syntax, keywords, operators, and built-in objects
- Web page interaction includes manipulating the DOM for dynamic content
- Web applications involve creating responsive web apps and handling JSON data
Including Scripts
- JavaScript code can be included directly in an HTML document using
<script>tags
Inline JavaScript
- Inserted directly within
<script>tags in an HTML document - Example:
<script> document.getElementById( 'message' ).innerText = 'Hello World!' </script> - Can be placed in the
<head>section (not recommended for large scripts, as it can slow performance), the<body>section (may slow down page rendering), or at the end of the<body>section (best practice for ensuring the page loads before scripts run)
External JavaScript
- Can be written in external plain text files with a
.jsextension - Included using the
<script>tag with thesrcattribute, like<script src="external_script.js"></script>
Benefits of External JavaScript files
- Reusability: The same script is usable across multiple web pages
- Organization: Keeps HTML clean and separates content from behavior
- Easier maintenance: Updating the
.jsfile updates all linked pages - .js files should only contain JavaScript code, without
<script>tags
Console Output
- JavaScript can dynamically write content into an HTML element using the
innerTextproperty to insert text into the element with the specifiedid - JavaScript can display output using a pop-up alert with the
alert()method - Used for debugging, can display content in the browser's JavaScript console
JavaScript Statements
- JavaScript code is composed of a series of instructions called "statements", which are generally executed in top-to-bottom order
- Each statement may contain: Keywords, Operators, Values, and Expressions
Semicolons
- Required in earlier JavaScript to terminate every statement, they are now optional unless multiple statements are on the same line
- Some developers still prefer using semicolons for clarity
Whitespace
- JavaScript ignores extra spaces, tabs, and line breaks and promotes readability
- total = 100 + 200; considered more readable than total=100+200;
Expressions and Statements
- Term produces a value used in calculations, function returns, etc.
- An expression is (80 + 20) → 100
- A statement performs an action that declares variables or running loops, like let total = 300;
JavaScript Syntax
- The rules that govern the JavaScript language
- Statements are often grouped with curly brackets {} inside function blocks that allow resuable execution when required
- It is good practice to indent statements by two spaces for better readability
JavaScript Values
- Fixed Values (Literals) include Integer numbers (100) or floating-point numbers (3.142)
- String literals are text enclosed in single ('JavaScript Fun') or double ("JavaScript Fun") quotes
Variables
- Created using the JavaScript let keyword, e.g.
let totalcreates a variable named "total" - Has a value thats assigned using the JavaScript = assignment operator, let total = 300
Expressions and Operators
- An expression produces a single value by combining values and operators and can be let result = (80 + 20)
- Expressions can have variables assigned let newTotal = (total - 200)
- finalValue = (100 + 50) * 2; result is 300
Case Sensitivity
- JavaScript is case-sensitive, variables total and Total are different
Comments
- Comments help explain code for better readability and debugging
//for single-line explains or/* ... */for longer explanation or disabling code during debugging
Variables
- A common container where data is stored and retrieved
- Easier to use because they are "loosely typed" to store any kind of data
Variable Types
- Strongly-typed languages must declare a specific data type before use like Java and C#
- Loosely-typed languages can store any data type without prior declaration like JavaScript
JavaScript Variables Declaring
- JavaScript Variables can be declared
- Automatically
- Using keyword "var"
- Using keyword "let"
- Using keyword "const"
Variable type considerations
- In the first example, if x, y, and z are undeclared variables they will get automatically declared when first used
- The var keyword was used in all JavaScript code from 1995 to 2015, but should only be used in code written for older browsers
- The
letandconstkeywords were added to JavaScript in 2015, which variables declared withletcan be reassigned new values as the script proceeds - can declare without a value assigned later using,
let myNumber, howeverconstis constant values and cannot be changed - use const if the type should not be changed (Arrays and Objects) - JavaScript sets the variable type according to value assigned and current variable type is revealed by using the
typeofkeyword
Functions
- A javascript block of code meant to return a single value
- A Block of code meant ot perform a particular task
- Is executed/invoked when something calls it
Function Syntax
- Declared with function Name()
- The name can have digits, letters, underscores and dollar signs
- Has parentheses containing parameters
- The code that the function runs is inisde the curly brackets
- Arguments behave as local variables inside the function block
Function Invocation
- Occurs when the user clicks an even like a button
- When javascript code calls on it
- You can run it autoamtically yourself
Function Return
- When script reaches the return, it will end execution
- After finishing the run the javascript returns to statement that called the function
- functions returns a value back to user
Assigning Functions to Variables
- Functions assigned to variables include named functions, anonymous expressions
- In self-invoking functions widely used, example code is executes when the script is first loaded
Function Hoisting
- Reads script in two sweeps with sweep 1 finding function declarations and hoists" them to the top
- Execution of the script is sweep 2
- The definitions are found before they are defined
- Function expressions are NOT hoisted
Scope
- Determines where variables are accessible in the script with JavsScript uing a Lexical scope
- Global scope outside functions and Local scope Inside Functions
Scope Types
- Global Scope can be found outside of functions,
- A global variable is declared outside of any function
- Can be accessed through entire script
- Is prone to naming conflict
- Local Scope can be found insdie function blocks and does not exist outsdie those blocks
Conversion Importance
- The language has different data types which causes errors when combined
- Some methods need strings ot numbers which requires conversion
Converting values
- Use parseInt() to converts string values to int
- "parseFloat(42abc)" gives "42.5" becausae it ignores alphabetic chracters
- With JavaScript, conversion to number fails and NaNs retured
- Use inNaN() check if string is a Number
- To return a Number use String() and toString() to convert
String() Notes
- "String (42)" gives "42’" as a number because converts a number to string
Arithmetic Operators
- Add (+), subtract (-), multiply (*), divide (/), modulus (%)
- Increment(++) and decrement(—)
- Exponentiation (**)
Assigning Values
=is the basic javascript value assignment
Short hand assigning
- Operators can perform operatons in a single step
- Add and assign (+=), subtract and assign (-=), multiply and assign (*=), divide and assign (/=)
- Modulus and assign (%=), Exponentiation and assign (**=)
Comparison Operators
- Evaluates conditions through comparison of 2 values
- Strict equality ("===") and Strict inequality ("!==") check both value and data type of operands
- Relational operators like (>, >=, <, <=) compare operators numerically
- Returns true if both value and type are equal like 25 === 25 results is false because of different types
- Returns true if the value or the type is different where 25 !== '25' results is true
Note when comparing
- The == and != operators allow type coercion, which can lead to unexpected results
- Always prefer === and !== for accurate comparisons
- The "> Returns true if the first operand is greater
- "< Returns true if the first operand is smalle
- ">= Returns true if the first operand is greater or equal
- "<=" Returns true if the first operand is smaller or equal
- Used frequently in loops and conditional statements
Ternary Operator
- Used for Evaluating functions and is shorthand
- The
condition ? expression_if_true : expression_if_falseconditional operator accepts 3 inputs
Summary
- Using "
- You can display output using
inAlertbox - Javascript statements are values, reserved words, expressions, and values
- Javascript interprester ingores tabls and spaces
- You can group a conditional inisde a curl bracked function
- When declaring a function:
- Use reserved word. number numbers, undescore to represent a function
- You must give a name
- Javascript has a vartiety of variable types such as "String", "Number", "Boolean", "Object", "Function", "Submbol"
letmeans you can reassign, whileconstmeans it should not change- Functions express returns singule valie with curly brackets. The parenthsis can be parameters
- Block includes a
returnstatement from acaller Calleris the one using()- When you call a function before it expression, its called hoisting
- Anonymous expressions do not have names and Lexical scope is where a variable is create that is global local or a closure
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
