no-float-calculation.md

Disallow floating point calculation

Since all JavaScript numbers are IEEE 754 floating point numbers, due to the binary nature of their encoding, some decimal numbers cannot be represented with perfect accuracy, so using floating point calculation in JavaScript is very dangerous (Related post).

Fail

0.1 + 2
'0.1' + 2
1 + 0.2
1 + '0.2'
0.1 + 0.2
'0.1' + 0.2
0.1 + '0.2'
'0.1' + '0.2'

0.1 - 2
'0.1' - 2
1 - 0.2
1 - '0.2'
0.1 - 0.2
'0.1' - 0.2
0.1 - '0.2'
'0.1' - '0.2'

0.1 * 2
'0.1' * 2
1 * 0.2
1 * '0.2'
0.1 * 0.2
'0.1' * 0.2
0.1 * '0.2'
'0.1' * '0.2'

0.1 * 2
'0.1' * 2
1 * 0.2
1 * '0.2'
0.1 * 0.2
'0.1' * 0.2
0.1 * '0.2'
'0.1' * '0.2'

0.1 + null
0.1 + false

amount + 0.1
amount - 0.1
amount * 0.1
amount / 0.1

0.1 + amount
0.1 - amount
0.1 * amount
0.1 / amount

Pass

1 + 2
1 - 2
1 * 2
1 / 2

1 + 2 + 3
1 - 2 - 3
1 * 2 - 3
1 / 2 / 3

amount + 1
amount - 1
amount * 1
amount / 1

1 + amount
1 - amount
1 * amount
1 / amount