JavaScript で +0 と -0 を判別する - Qiita

function isNegativeZero(x) { return x === 0 && new Uint8Array(new Float32Array([ x ]).buffer)[3] === 128; } function isPositiveZero(x) { return x === 0 && new Uint8Array(new Float32Array([ x ]).buffer)[3] === 0; }