x >= x pattern in JavaScript

When reading source of D3.js I saw x >= x pattern. If it is for detecting NaNs among numbers, why not just isNaN(x) or x == x? Source, where I encountered it: d3.min = function(array, f) { var i = -1, n = array.length, a, b; if (arguments.length === 1) { while (++i < n) if ((b = array[i]) != null && b >= b) { a = b; break; } while (++i < n) if ((b = array[i]) != null && a > b) a = b; } else { whil

[igrep]

“x >= x”で比較するとundefinedかどうかも確認できる、とな。型が守ってくれないと辛いね。