constants to the left



~1 min read


162 words

Hear ye, hear ye, by royal decree, I hereby declare: when evaluating, put constants on the left

Okay, so this isn’t actually a decree and shouldn’t be followed dogmatically, but having been burned before due to an accidental assignment (where a comparison was intended), following this rule seems sensible.

What it looks like:

0 == x // do this
x == 0 // not this

Now, if you were to mistype and put:

0 = x

You get an error message immediately instead of a silent bug:

Uncaught SyntaxError: Invalid left-hand side in assignment

Filing this under other practical advice I’ve found for avoiding the avoidable, like not using the greater than symbol.

Update: Interestingly, during a code review, my use of this was actually called out as non-idiomatic. While I was able to defend my reasoning for placing the constants on the left, it’s worth remembering that it may require a bit of education.

Hi there and thanks for reading! My name's Stephen. I live in Chicago with my wife, Kate, and dog, Finn. Want more? See about and get in touch!