Type Conversion

Converts a value, like a string, into a number data type.

Part of: JavaScript Coding without HTML and CSS — Module 10, ACARA Digital Technologies Years 7–8 — Programming with Control Structures and Functions (JavaScript) — Module 23

Understanding Type Conversion in JavaScript

What it does: Boolean() converts values like 1 into the boolean true. This converts the variable input into a number. Number() turns a value, like a string, into a number type. JavaScript requires a capital N: Number(). Number(x), String(x), and Boolean(x) all need parentheses. JavaScript's built-in function is Number(), not number(). Without parentheses, this isn't a valid function call.

Common mistakes: 'Number' must start with a capital N, not lowercase. 'String' must start with a capital S, not lowercase.

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Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

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This module's key terms are also in a printable crossword (Modules 1–10) and word search (Modules 1–29).

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Learning

Duo

Does Number() convert a value into a number?

YesNo

Matches

let n = number("5");

↓

Wrong - 'Number' must start with a capital N

Applying

Meanings

Term

Number()

Meaning

Converts a value, like a string, into a number data type.

Practice

let age = 12;

Testing

Gaps

let ageText = (age);

Check Answer

Spots

1let num = "5";

2let x = number(num);

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Quick Questions

1. Does Number() convert a value into a number?

A. No

B. Yes ✓

Number() turns a value, like a string, into a number type.

2. Does String() convert a value into a string?

A. Yes ✓

B. No

String() turns a value, like a number, into a string type.

3. Is 'number' with a lowercase n a valid conversion function?

A. No ✓

B. Yes

JavaScript requires a capital N: Number().

4. Does Boolean() convert a value into true or false?

A. No

B. Yes ✓

Boolean() converts values into the boolean true or false.

5. Do type conversion functions need parentheses around the value?

A. Yes ✓

B. No

Number(x), String(x), and Boolean(x) all need parentheses.

Match the Pairs

Number("5") → Converts the string "5" into the number 5

String(12) → Converts the number 12 into the string "12"

Converts a value into true or false → Boolean(1)

Turns text into a number data type → Number(input)

let n = number("5"); → Wrong - 'Number' must start with a capital N

let text = String age; → Wrong - String() needs parentheses around the value

Key Term

Number()

Converts a value, like a string, into a number data type.

Fill in the Blanks

1. let ageText = String(age);

Hint: Type the function that converts a value to a string.

2. let num = Number(input);

Hint: Type the function that converts a value to a number.

3. let flag = Boolean(1);

Hint: Type the function that converts a value to a boolean.

4. let count = Number("8");

Hint: Type the function that converts a value to a number.

5. let label = String(score);

Hint: Type the function that converts a value to a string.

Spot the Error

Question 1

A let num = "5";

B let x = number(num);

C console.log(x);

Line B — 'Number' must start with a capital N, not lowercase.

Question 2

A let age = 12;

B console.log(text);

C let text = string(age);

Line C — 'String' must start with a capital S, not lowercase.

Question 3

A let b = boolean(val);

B let val = 1;

C console.log(b);

Line A — 'Boolean' must start with a capital B, not lowercase.

Question 4

A let s = "9";

B let n = Number(s);

C let m = Numbr(s);

Line C — 'Number' is misspelled as 'Numbr'.

Question 5

A let age = 20;

B let txt2 = Sting(age);

C let txt = String(age);

Line B — 'String' is misspelled as 'Sting'.

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