JavaScript basics · Lesson 10 of 12 · 7 minutes

JavaScript basics: Function parameters

Parameters let the same function work with different inputs without duplicating its body.

Open the lab Course map

Mastery 0/3Run itExplain itApply it

Current edit

PreviewNo external resources

Your objectives

Hints are always available. Wrong turns never cost XP.

1
Build function parameters
Build this first target: the JavaScript statements shown in the example, as executable-position code rather than a string or comment. Explain how the values and control flow implement this lesson’s concept; this browser lab checks structure without executing arbitrary JavaScript.
Hint & worked example
Parameters let the same function work with different inputs without duplicating its body.
The requested statements are present as code, not inside a string or comment. No arbitrary JavaScript is executed.
```
function label(name) { return "Lesson: " + name; }
```
Common mistake to avoid: A string containing code executes automatically when it is assigned.
2
Extend the function parameters example
Extend your file to include: the JavaScript statements shown in the example, as executable-position code rather than a string or comment. Explain how the values and control flow implement this lesson’s concept; this browser lab checks structure without executing arbitrary JavaScript.
Hint & worked example
Parameters let the same function work with different inputs without duplicating its body.
The requested statements are present as code, not inside a string or comment. No arbitrary JavaScript is executed.
```
function label(name) { return "Lesson: " + name; }
const paths = label("Paths");
```
Common mistake to avoid: A successful element lookup guarantees that the rest of an event handler is correct.
3
Verify the complete function parameters pattern
Finish the pattern with: the JavaScript statements shown in the example, as executable-position code rather than a string or comment. Explain how the values and control flow implement this lesson’s concept; this browser lab checks structure without executing arbitrary JavaScript.
Hint & worked example
Parameters let the same function work with different inputs without duplicating its body.
The requested statements are present as code, not inside a string or comment. No arbitrary JavaScript is executed.
```
function label(name) { return "Lesson: " + name; }
const paths = label("Paths");
const logs = label("Logs");
```
Common mistake to avoid: A string containing code executes automatically when it is assigned.

Understand the pattern

Parameters let the same function work with different inputs without duplicating its body.

Misconceptions to reject

A string containing code executes automatically when it is assigned.
A successful element lookup guarantees that the rest of an event handler is correct.

This is a code-inspection lab, not a full JavaScript runtime.

Worked example and expected result

function label(name) { return "Lesson: " + name; }
const paths = label("Paths");
const logs = label("Logs");

Parameters let the same function work with different inputs without duplicating its body.

Try a variation

Adapt the final example to a different project name while retaining its structure and relationships. A different context still needs a real browser and accessibility check.

Explain it

Which statement correctly explains function parameters?A successful element lookup guarantees that the rest of an event handler is correct.Parameters let the same function work with different inputs without duplicating its body.A string containing code executes automatically when it is assigned.

Apply it elsewhere

You reuse function parameters in a different project. What must still be verified?The input values, element availability, and actual behavior in a real browser.Nothing; passing a single exercise guarantees every future use.Only whether the source code has the same number of lines.

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: JavaScript basics: Return values Try an incident drill

Anonymous lesson and mastery progress lasts for this session. Sign in to keep synced lesson XP between sessions; mastery stays device-local. No speed bonus, lost lives, or hint penalties.

Keep learning

MDN: JavaScript fundamentals