JavaScript Data Types and Conversions Quiz

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Question 1/15

How do you correctly check if a variable is a string in JavaScript?

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Question 2/15

What will `"5" + 1` evaluate to in JavaScript? 
"5" + 1

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Question 3/15

In JavaScript, which type of loop will run at least once no matter what?

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Question 4/15

What does the `===` operator compare?

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Question 5/15

What is the value of `Boolean("false")` in JavaScript? 
Boolean("false")

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Question 6/15

What value is returned by the expression `Number(undefined)` in JavaScript? 
Number(undefined)

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Question 7/15

What does `parseInt("10.5")` return in JavaScript? 
parseInt("10.5")

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Question 8/15

How can you express the floating-point number 12.5 using scientific notation in JavaScript?

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Question 9/15

What is the result of `"5" - 1` in JavaScript? 
"5" - 1

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Question 10/15

What will `Boolean(" ")` return? 
Boolean(" ")

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Question 11/15

Which JavaScript function would you use to combine variable `let a = 'Hello'; let b = 'World';` into a single output 'Hello World'? 
let a = 'Hello';
let b = 'World';

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Question 12/15

What is the value of `Number('123abc')` in JavaScript? 
Number('123abc')

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Question 13/15

How do you convert a string `"123"` to a number in JavaScript?

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Question 14/15

How can you check if a number is not a number using a built-in JavaScript function?

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Question 15/15

Which of the following is NOT a falsy value in JavaScript?

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Your Answers

Question 1/15
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How do you correctly check if a variable is a string in JavaScript?

Available answers

Use `typeof variable === 'string'` to check if a variable is of type string properly.
Question 2/15
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What will `"5" + 1` evaluate to in JavaScript? 
"5" + 1

Available answers

In JavaScript, when using the + operator with a string and a number, the number is converted to a string, and string concatenation occurs. Thus, `"5" + 1` evaluates to `"51"`.
Question 3/15
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In JavaScript, which type of loop will run at least once no matter what?

Available answers

A `do...while` loop will execute the block of code at least once before checking the condition.
Question 4/15
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What does the `===` operator compare?

Available answers

The `===` operator in JavaScript checks for both value and type equality.
Question 5/15
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What is the value of `Boolean("false")` in JavaScript? 
Boolean("false")

Available answers

When a string that is not empty (including the string "false") is converted to a boolean in JavaScript, it results in `true`. Non-empty strings are truthy values.
Question 6/15
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What value is returned by the expression `Number(undefined)` in JavaScript? 
Number(undefined)

Available answers

The `Number` function converts the value to a number. If it can't be converted to a number, it will return `NaN`. `undefined` is converted to `NaN`.
Question 7/15
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What does `parseInt("10.5")` return in JavaScript? 
parseInt("10.5")

Available answers

The `parseInt` function converts a string to an integer. It parses up to the first invalid character for an integer, so `parseInt("10.5")` returns `10`.
Question 8/15
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How can you express the floating-point number 12.5 using scientific notation in JavaScript?

Available answers

In JavaScript, `1.25e1` is equal to `12.5`, where `e1` represents 10 to the power of 1.
Question 9/15
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What is the result of `"5" - 1` in JavaScript? 
"5" - 1

Available answers

In JavaScript, the `-` operator converts operands to numbers if they're not, so `"5" - 1` evaluates to `4`.
Question 10/15
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What will `Boolean(" ")` return? 
Boolean(" ")

Available answers

The `Boolean` conversion of any non-empty string will return `true`, including a space character.
Question 11/15
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Which JavaScript function would you use to combine variable `let a = 'Hello'; let b = 'World';` into a single output 'Hello World'? 
let a = 'Hello';
let b = 'World';

Available answers

In JavaScript, you use `a.concat(' ', b)` to combine two strings.
Question 12/15
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What is the value of `Number('123abc')` in JavaScript? 
Number('123abc')

Available answers

The `Number` function returns `NaN` when a string cannot be converted to a number. Since `'123abc'` is not a valid number, the result is `NaN`.
Question 13/15
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How do you convert a string `"123"` to a number in JavaScript?

Available answers

You can convert a string to a number using the `Number` function, like so: `Number("123")`.
Question 14/15
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How can you check if a number is not a number using a built-in JavaScript function?

Available answers

The `isNaN` function checks whether a value is `NaN`. If the result of the expression is `NaN`, `isNaN` returns `true`.
Question 15/15
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Which of the following is NOT a falsy value in JavaScript?

Available answers

In JavaScript, the string "false" is not falsy. Falsy values include `false`, `0`, `NaN`, `""` (empty string), `null`, and `undefined`.