Podcast
Questions and Answers
What will be the result of the expression '3 * 2'?
What will be the result of the expression '3 * 2'?
- 6 (correct)
- 1
- 3
- 5
Which operator would you use to increment a variable by 1?
Which operator would you use to increment a variable by 1?
- +=
- +
- --
- ++ (correct)
What is the standardized version of JavaScript called?
What is the standardized version of JavaScript called?
- ECMAScript (correct)
- JScript
- JavaScript Standard Edition
- NetscapeScript
What is the output of the expression '3 + 2'?
What is the output of the expression '3 + 2'?
What is the primary reason Netscape's JavaScript had to be standardized?
What is the primary reason Netscape's JavaScript had to be standardized?
What does the expression 'x < y' evaluate to if x = 2 and y = 3?
What does the expression 'x < y' evaluate to if x = 2 and y = 3?
Which version of ECMAScript was in stable use across web browsers for about a decade?
Which version of ECMAScript was in stable use across web browsers for about a decade?
What is the output of the expression 'count *= 3' if count is initially 2?
What is the output of the expression 'count *= 3' if count is initially 2?
What is the version number of the V8 JavaScript engine mentioned?
What is the version number of the V8 JavaScript engine mentioned?
Which JavaScript version corresponds to ECMAScript 3?
Which JavaScript version corresponds to ECMAScript 3?
What is the result of 'false == (x > y)' when x = 2 and y = 3?
What is the result of 'false == (x > y)' when x = 2 and y = 3?
Which version of ECMAScript was developed but never released due to being too ambitious?
Which version of ECMAScript was developed but never released due to being too ambitious?
What is the result of the expression '!(x == y)' when x = 2 and y = 3?
What is the result of the expression '!(x == y)' when x = 2 and y = 3?
Which of the following is a correct way to perform subtraction in JavaScript?
Which of the following is a correct way to perform subtraction in JavaScript?
What is Microsoft's implementation of JavaScript formally known as?
What is Microsoft's implementation of JavaScript formally known as?
Which version of ECMAScript is mentioned as being the most recent at the time of writing?
Which version of ECMAScript is mentioned as being the most recent at the time of writing?
What happens when the browser supports localStorage and there is stored data?
What happens when the browser supports localStorage and there is stored data?
What is the purpose of the getLenders function?
What is the purpose of the getLenders function?
Which object is used to make an asynchronous HTTP request in the getLenders function?
Which object is used to make an asynchronous HTTP request in the getLenders function?
What is the first step when the getLenders function is called?
What is the first step when the getLenders function is called?
What does the function do if the browser does not support XMLHttpRequest?
What does the function do if the browser does not support XMLHttpRequest?
What format does the getLenders function use to send user data to the server?
What format does the getLenders function use to send user data to the server?
How is the user input encoded in the URL for the request?
How is the user input encoded in the URL for the request?
What is indicated by the comment about 'asynchronous programming' in the context of client-side JavaScript?
What is indicated by the comment about 'asynchronous programming' in the context of client-side JavaScript?
What distinguishes an expression from a statement in programming?
What distinguishes an expression from a statement in programming?
What is a characteristic of a function in JavaScript?
What is a characteristic of a function in JavaScript?
How is a method defined in JavaScript?
How is a method defined in JavaScript?
What does the 'this' keyword refer to within a method in JavaScript?
What does the 'this' keyword refer to within a method in JavaScript?
In the provided example, what does the plus1 function return when invoked with an argument of 3?
In the provided example, what does the plus1 function return when invoked with an argument of 3?
What happens when you invoke square(plus1(y)) if y is 3?
What happens when you invoke square(plus1(y)) if y is 3?
What is the primary purpose of control structures in programming?
What is the primary purpose of control structures in programming?
What does the push() method do when invoked on an array in JavaScript?
What does the push() method do when invoked on an array in JavaScript?
What does the value null
convert to when changed to a Boolean?
What does the value null
convert to when changed to a Boolean?
Which of the following values converts to NaN
when turned into a number?
Which of the following values converts to NaN
when turned into a number?
What is the numeric conversion result of the string '1.2'?
What is the numeric conversion result of the string '1.2'?
How does the value {} (any object)
convert when treated as a string?
How does the value {} (any object)
convert when treated as a string?
What does the value false
convert to when coerced into a number?
What does the value false
convert to when coerced into a number?
Which of the following values converts to true
when evaluated as a Boolean?
Which of the following values converts to true
when evaluated as a Boolean?
What happens when attempting to convert undefined
to a number?
What happens when attempting to convert undefined
to a number?
Study Notes
JavaScript History and Versions
- JavaScript was initially developed at Netscape.
- “JavaScript” is a trademark licensed by Sun Microsystems (now Oracle) for Netscape’s (now Mozilla’s) implementation.
- The standardized version of the language is called ‘ECMAScript’ due to trademark restrictions.
- Microsoft’s version of JavaScript is called ‘JScript.’
- Generally, the language is referred to as JavaScript.
- This book uses ‘ECMAScript’ to refer to the language standard.
Major ECMAScript Versions
- All web browsers currently implement version 3 of the ECMAScript standard (ES3).
- A new version of the language, ECMAScript version 5 (ES5), has been defined and is being adopted by browsers.
- This book covers both ES3 and ES5 features.
JavaScript Version Numbers
- ECMAScript versions 3 and 5 are relevant for the language itself.
- Version 4 of ECMAScript was developed but never released.
- Mozilla uses its own version numbers, starting with 1.5, which is essentially ECMAScript 3.
- Mozilla’s later versions include nonstandard language extensions.
- JavaScript interpreters have their own version numbers. For example, Google’s V8 interpreter is currently at version 3.0.
Arithmetic Operators
- Operators like addition (+), subtraction (-), multiplication (*), and division (/) are common.
- Shorthand arithmetic operators (++, --, +=, *=) provide concise ways to increment, decrement, and modify values.
Equality and Relational Operators
- Operators like == (equality), != (inequality), < (less than), > (greater than), <= (less than or equal), >= (greater than or equal) compare values.
- They return true or false based on the comparison result.
- String comparisons use alphabetical order.
Logical Operators
- Logical operators combine or invert boolean values.
&&
(AND) returns true only if both operands are true.||
(OR) returns true if at least one operand is true.!
(NOT) inverts a boolean value.
Functions
- Functions are blocks of code that can be invoked repeatedly.
- Defined using the
function
keyword, a name, and parameters enclosed in parentheses. - Functions can return values.
- Can be assigned to variables.
- When functions are assigned to object properties, they are called ‘methods.’
Methods and Objects
- All JavaScript objects have built-in methods (e.g.,
push()
for arrays). - Methods can be defined for custom objects.
- The
this
keyword refers to the object on which the method is defined.
Client-Side JavaScript and XMLHttpRequest
- JavaScript code can interact with the server using
XMLHttpRequest
objects. - Functions can be used to fetch data from URLs.
- Asynchronous programming (e.g., handling server responses) is common in client-side JavaScript.
JavaScript Type Conversions
- JavaScript automatically converts values between data types (e.g., strings, numbers, booleans, objects).
- Conversion to string is well-defined for all primitive values.
- Conversion to boolean follows specific rules (e.g., true converts to 1, false and the empty string "" convert to 0).
- Number conversions are complex, with strings that can be parsed as numbers converting to those numbers.
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Description
Explore the origins and developments of JavaScript, from its initial creation at Netscape to its various versions like ECMAScript. Understand the differences between ES3 and ES5 and the reason why some versions, like ES4, were never released. This quiz will enhance your knowledge of the JavaScript language standard.