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Questions and Answers
Which of the following correctly represents the string type in JavaScript?
Which of the following correctly represents the string type in JavaScript?
What does the value 'null' represent in JavaScript?
What does the value 'null' represent in JavaScript?
What indicates that a variable has not been assigned a value?
What indicates that a variable has not been assigned a value?
What will the expression '11 > 7' return in JavaScript?
What will the expression '11 > 7' return in JavaScript?
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What is the output of 'typeof null' in JavaScript?
What is the output of 'typeof null' in JavaScript?
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Which statement regarding the number type in JavaScript is true?
Which statement regarding the number type in JavaScript is true?
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Which of the following values is considered NaN (Not a Number) in JavaScript?
Which of the following values is considered NaN (Not a Number) in JavaScript?
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Which statement about booleans in JavaScript is correct?
Which statement about booleans in JavaScript is correct?
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What is a primary characteristic that differentiates JavaScript from Java?
What is a primary characteristic that differentiates JavaScript from Java?
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Which ECMAScript version was abandoned?
Which ECMAScript version was abandoned?
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How can JavaScript programs be embedded in an HTML document?
How can JavaScript programs be embedded in an HTML document?
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What is the role of the Math object in JavaScript?
What is the role of the Math object in JavaScript?
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Which of the following statements about JavaScript syntax is correct?
Which of the following statements about JavaScript syntax is correct?
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What is a primary use of the JavaScript DOM?
What is a primary use of the JavaScript DOM?
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Which of the following best describes the use of the 'alert' function in JavaScript?
Which of the following best describes the use of the 'alert' function in JavaScript?
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In what scenario would you typically use local storage in JavaScript?
In what scenario would you typically use local storage in JavaScript?
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Which statement best describes the purpose of a variable in JavaScript?
Which statement best describes the purpose of a variable in JavaScript?
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Which declaration is considered correct for multiple variables in one line?
Which declaration is considered correct for multiple variables in one line?
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What is the purpose of the const keyword in variable declaration?
What is the purpose of the const keyword in variable declaration?
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Which of the following is NOT a valid variable name in JavaScript?
Which of the following is NOT a valid variable name in JavaScript?
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What will be the result of the following operation: let a = 10; a += 5;?
What will be the result of the following operation: let a = 10; a += 5;?
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What does the expression '8 % 3' evaluate to?
What does the expression '8 % 3' evaluate to?
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Which of the following describes the camelCase naming convention in JavaScript variables?
Which of the following describes the camelCase naming convention in JavaScript variables?
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In JavaScript, what does the command 'alert(5 % 2)' produce?
In JavaScript, what does the command 'alert(5 % 2)' produce?
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What does the expression 'a % b' return?
What does the expression 'a % b' return?
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Which operation is NOT a unary operation?
Which operation is NOT a unary operation?
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Which of the following methods returns a pseudorandom number?
Which of the following methods returns a pseudorandom number?
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In prefix notation, how would you increment the variable 'a' by 1?
In prefix notation, how would you increment the variable 'a' by 1?
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Which statement is TRUE about JavaScript primitive data types?
Which statement is TRUE about JavaScript primitive data types?
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Which operation is an example of a binary operation?
Which operation is an example of a binary operation?
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How can you retrieve the absolute value of a number 'x' in JavaScript?
How can you retrieve the absolute value of a number 'x' in JavaScript?
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What will the following code output: console.log('a = ' + 5); ?
What will the following code output: console.log('a = ' + 5); ?
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Study Notes
JavaScript Data Types
- JavaScript has three types of quotes:
- Double quotes: "Hello"
- Single quotes: 'Hello'
- Backticks:
Hello
Number
- Number type represents both integers and floating point numbers
- Special numeric values include:
- Infinity:
alert( 1 / 0 )
- NaN (Not a Number):
alert( "not a number" / 2 + 5 )
- Infinity:
Boolean
- Represents logical type with two values:
true
andfalse
- Used for yes/no values,
true
represents "yes" andfalse
"no" -
true
is assigned tonameFieldChecked
when the field is checked -
false
is assigned toageFieldChecked
when the field is not checked
Null
-
null
is a special value representing "nothing", "empty" or "value unknown"
Undefined
-
undefined
indicates a value has not been assigned - If a variable is declared but not assigned, its value will be
undefined
typeof Operator
- The
typeof
operator returns the type of the argument - Two forms of syntax:
- As an operator:
typeof x
- In parentheses:
(typeof x)
- As an operator:
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Description
Test your knowledge of JavaScript data types including strings, numbers, booleans, null, and undefined. This quiz will help reinforce your understanding of how these data types work and their specific uses in JavaScript programming.