Using Boolean prefixes for variables

if (monday) {
  // `monday` could be the date of next Monday. You wouldn’t expect this to
  // be `true` or `false`.
}

if (isMonday) {
  // This reads like the question “is Monday?”, which you would answer with
  // “yes” or “no”. The name tells you that this has to be Boolean.
}


if (children) {
  // `children` could be a list of names or whether a person has children or
  // not. It’s difficult to tell if this is an array or a Boolean.
}

if (hasChildren) {
  // You can only read this as “has children?”, which is either `true` or
  // `false`. Ideally.
}


if (rocks) {
  // Could be the name of your favorite rocks, like “The” or “30”.
}

if (doesRock) {
  // This does rock, `true`. Note how it’s not called `doesRocks`, which
  // would read a little awkward.
}