JavaScript basics · Lesson 12 of 12 · 10 minutes

JavaScript basics: Template strings

Backtick template strings can interpolate expressions with ${...}; ordinary quoted strings do not interpolate them.

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 template strings
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
Backtick template strings can interpolate expressions with ${...}; ordinary quoted strings do not interpolate them.
The requested statements are present as code, not inside a string or comment. No arbitrary JavaScript is executed.
```
const completed = 3;
```
Common mistake to avoid: A string containing code executes automatically when it is assigned.
2
Extend the template strings 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
Backtick template strings can interpolate expressions with ${...}; ordinary quoted strings do not interpolate them.
The requested statements are present as code, not inside a string or comment. No arbitrary JavaScript is executed.
```
const completed = 3;
const total = 10;
```
Common mistake to avoid: A successful element lookup guarantees that the rest of an event handler is correct.
3
Verify the complete template strings 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
Backtick template strings can interpolate expressions with ${...}; ordinary quoted strings do not interpolate them.
The requested statements are present as code, not inside a string or comment. No arbitrary JavaScript is executed.
```
const completed = 3;
const total = 10;
const message = `${completed} of ${total} lessons complete`;
```
Common mistake to avoid: A string containing code executes automatically when it is assigned.

Understand the pattern

Backtick template strings can interpolate expressions with ${...}; ordinary quoted strings do not interpolate them.

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

const completed = 3;
const total = 10;
const message = `${completed} of ${total} lessons complete`;

Backtick template strings can interpolate expressions with ${...}; ordinary quoted strings do not interpolate them.

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 template strings?A string containing code executes automatically when it is assigned.A successful element lookup guarantees that the rest of an event handler is correct.Backtick template strings can interpolate expressions with ${...}; ordinary quoted strings do not interpolate them.

Apply it elsewhere

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

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Review this course 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

01JavaScript basics: Return valuesreturn supplies a result to the caller. A function without an executed return yields undefined.Practice

MDN: JavaScript fundamentals