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WEB-DEVELOPMENT-APPLICATIONS Practice Questions

Try 10 free WEB-DEVELOPMENT-APPLICATIONS exam-style questions for WGU Web Development Applications certification exam. Check each answer and review the explanation and source references.

Exam code: WEB-DEVELOPMENT-APPLICATIONS
Provider: WGU
Free questions: 10
Full set: 131 questions
Last update check: October 18, 2026

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Given the following JavaScript code: ```javascript var n1 = 10; var n2 = "20.39"; ``` Which function should a developer use to convert the content of the variable `n2` from a string to a number while keeping the decimal places?

Answer options

Correct Answer:

Explanation

The parseFloat() function is the correct choice because it parses a string argument and returns a floating-point number. Unlike parseInt(), it recognizes and preserves the decimal part of a number represented in a string. In this case, parseFloat("20.39") will correctly evaluate to the number 20.39. This function stops parsing when it encounters a character that is not part of the number format, which makes it robust for this specific task.

Why Incorrect

A. isNaN is a function that checks if a value is "Not-a-Number"; it does not perform any type conversion.

B. parseInt converts a string to an integer, truncating any decimal places. It would incorrectly return 20.

D. toUpperCase is a string method that converts a string to uppercase letters; it is irrelevant for number conversion.

References

- Mozilla Developer Network (MDN). (2023). parseFloat(). Global Objects. Retrieved from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/GlobalObjects/parseFloat (See the main description and first example).

- Haverbeke, M. (2018). Eloquent JavaScript (3rd ed.). No Starch Press. Chapter 3: Functions, Section "Optional Arguments". (Discusses number conversion functions).

- MIT OpenCourseWare. (2016). 6.170 Software Studio, Lecture 10: JavaScript. Retrieved from https://ocw.mit.edu/courses/6-170-software-studio-spring-2016/resources/mit6170s16lec10/ (Covers JavaScript's type system and conversion functions).

Question breakdown

Tests: Convert strings to numbers in JavaScript
Difficulty: Easy

Key idea: parseFloat() parses a string and returns a floating-point number, keeping the fractional part.

How to reach the answer

The variable n2 holds the string "20.39".
The requirement is to keep the decimal places, so an integer-only conversion is ruled out.
parseInt would return 20 and drop .39.
parseFloat("20.39") returns 20.39, which meets the requirement.

Each option

AIncorrect. isNaN only tests whether a value is Not-a-Number and returns a boolean; it converts nothing.
BIncorrect. parseInt returns an integer, so the decimal portion .39 is lost.
CCorrect. parseFloat returns a floating-point number, so "20.39" becomes 20.39.
DIncorrect. toUpperCase is a string method that changes letter case; it returns a string, not a number.

Common trap: parseInt looks like the generic way to turn a string into a number, but it discards everything after the decimal point.

In practice: Values read from form inputs or query strings arrive as strings. Prices, measurements, and similar values need parseFloat (or Number) before you do arithmetic on them.

Remember: Use parseFloat to keep decimals and parseInt when you want a whole number.

Drafted with AI assistance and checked against the answer key.

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