TypeError: assignment to a constant variable

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. A student writes const score = 0; then score = 10; What happens when the code runs?

A TypeError: Assignment to constant variable

B score becomes 10 with no error

2. Which declaration lets you change the value later without an error?

A let lives = 3;

B const lives = 3;

3. The console shows: TypeError: Assignment to constant variable. What is the cause?

A The code tried to reassign a const variable

B The code forgot a semicolon at the end of a line

4. Which code will cause a TypeError?

A let total = 5; total = total + 1;

B const total = 5; total = total + 1;

5. How do you fix this code? const count = 0; count++;

A Change count++ to count--

B Change const to let

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1TypeError: Assignment to constant variable.		Alet lives = 3; lives = 2;
2let score = 0; score = 5;		Bname holds a string, not a function, so calling it with () causes a TypeError. Only call names that are functions.
3Reassigning a const variable causes a TypeError		Cconst lives = 3; lives = 2;
4Fix the error by changing const to let when the value must change		DA variable declared with let can be given a new value, so no TypeError happens.
5const points = 10; points += 5;		Epoints is a const, so += tries to give it a new value and causes a TypeError. Declare it with let instead.
6const name = "Sam"; name();		FThe error JavaScript shows when code tries to give a new value to a const variable.

Definitions

TypeError: Assignment to constant variable

Fill in the Blanks

Complete each line of code by filling in the missing parts.

___ score = 0; score = score + 5;

const lives = 3; lives = 2; // Error type: _________

const name = "Sam"; name(); // TypeError: ____ is not a function

const lives = 3; lives = 2; // TypeError: Assignment to ________ variable

_____ PI = 3.14159; console.log(PI);

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A const name = "Ava";

B console.log(name);

C const score = 0;

D score = score + 10;

Question 2

A const MAX_LIVES = 3;

B const lives = MAX_LIVES;

C lives--;

D console.log(lives);

Question 3

A let count = 0;

B const limit = 3;

C while (count < limit) {

D limit += 1;

E }

Question 4

A const price = 5;

B price = price + 2;

C console.log(price);

Question 5

A const age = 12;

B console.log(age());

C console.log(age + 1);

Answer Key

TypeError: assignment to a constant variable

Section A: Quick Questions

A — TypeError: Assignment to constant variable

A — let lives = 3;

A — The code tried to reassign a const variable

B — const total = 5; total = total + 1;

B — Change const to let

Section B: Match the Pairs

TypeError: Assignment to constant variable. → The error JavaScript shows when code tries to give a new value to a const variable.

let score = 0; score = 5; → A variable declared with let can be given a new value, so no TypeError happens.

Reassigning a const variable causes a TypeError → const lives = 3; lives = 2;

Fix the error by changing const to let when the value must change → let lives = 3; lives = 2;

const points = 10; points += 5; → points is a const, so += tries to give it a new value and causes a TypeError. Declare it with let instead.

const name = "Sam"; name(); → name holds a string, not a function, so calling it with () causes a TypeError. Only call names that are functions.

Section C: Definitions

TypeError: Assignment to constant variable — The error JavaScript shows when code tries to give a new value to a const variable. Fix it by declaring the variable with let if its value needs to change.

Section D: Fill in the Blanks

let score = 0;
score = score + 5;

const lives = 3;
lives = 2;
// Error type: TypeError

const name = "Sam";
name();
// TypeError: name is not a function

const lives = 3;
lives = 2;
// TypeError: Assignment to constant variable

const PI = 3.14159;
console.log(PI);

Section E: Spot the Error

C — score is given a new value on line 4, so it cannot be a const. Reassigning it gives TypeError: Assignment to constant variable. Declare it with let score = 0; instead.

B — lives-- changes the value, but a const cannot change. This causes TypeError: Assignment to constant variable. Use let lives = MAX_LIVES; because lives changes.

D — limit is a const, so adding to it causes TypeError: Assignment to constant variable. The loop should update the counter that changes, count += 1;

A — price is changed on line 2, so a const will throw TypeError: Assignment to constant variable. Use let price = 5; for values that change.

B — age holds a number, not a function, so the brackets () cannot call it. JavaScript shows TypeError: age is not a function. It should be console.log(age);