The three cases you state aren't nearly as hairy as determining whether something is a positive integer. Someone might do something like ~~n to truncate a floa

The three cases you state aren't nearly as hairy as determining whether something is a positive integer. Someone might do something like ~~n to truncate a float. That works fine until you go above 32 bits. Math.trunc should be used instead. Someone might do something like n >>> 0 === n, and using any bitwise operators will always bake in the assumption that the number is 32 bits. Do you treat negative 0 as a negative integer? Detecting negative 0 is hairy. So, to avoid bad patterns, it makes sense. For is-bigger-than-5(x), x > 5 is not hairy. For add-1-to-a-number(n), n + 1 is not hairy. For word-starts-with-capital-letter(word)? That one is actually pretty hairy. There are programmers that would write a regular expression /^[A-Z]/, or check the charCode of the first character being within the A-Z range, amongst other solutions. An appropriate solution, however, would be (typeof word == "string" && word.length && word[0] == word[0].toUpperCase() && word[0].toUpperCase() != word[0].toLowerCase()), because the toUpperCase and toLowerCase methods are unicode-aware, and presently you can't access unicode properties using Javascript's flavor of regular expressions.