Operations

JavaScript · Unit 1: First steps

+, -, * and / work like on a calculator.

Watch out for /: it gives the exact result, with decimals if there are any.

console.log(3 * 4);
console.log(7 / 2);

Prints

12
3.5

% gives what's left over from a division, and ** raises to a power.

7 % 2 is 1 because the 2 fits three times into the 7 and 1 is left over.

console.log(7 % 2);
console.log(2 ** 3);

Prints

1
8

Math.floor() cuts the decimals downwards and Math.round() rounds to the nearest whole number.

console.log(Math.floor(7 / 2));
console.log(Math.round(7 / 2));

Prints

3
4

Math.max() gives you the highest of the values you pass it and Math.min() the lowest.

console.log(Math.max(8, 3, 10));
console.log(Math.min(8, 3, 10));

Prints

10
3

First ** is worked out, then *, / and %, and + and - at the end.

Whatever goes inside parentheses is worked out before anything else.

console.log(10 - 2 * 3);
console.log((10 - 2) * 3);

Prints

4
24

Exercises in this lesson

You do them in the app, which checks them on the spot and explains why.

1. Predict the output

What does this code print?

const pizza = 7;
const people = 2;
console.log(pizza / people);

5. Predict the output

What does this code print?

console.log(Math.floor(4.7));
console.log(Math.round(4.7));

6. Complete the code

Fill in to print the highest grade.

const emma = 78;
const jack = 92;
console.log(Math.___(emma, jack));

7. Find the bug
This program should say how many hours and minutes 135 minutes are. Which line has the error?
```
const mins = 135;
const hours = mins / 60;
const rest = mins % 60;
console.log(hours, "h", rest, "min");
```
8. Predict the output
Multiplication goes before addition. What does it print?
```
console.log(2 + 3 * 4);
```
9. Find the bug
This program should print the average of 4 and 6. Which line has the error?
```
const a = 4;
const b = 6;
const average = a + b / 2;
console.log(average);
```

10. Predict the output

17 cookies are shared out among 5 kids. What does it print?

const cookies = 17;
const kids = 5;
const each = cookies / kids;
console.log(Math.floor(each));
console.log(cookies % kids);

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