JavaScript 数字取整函数：向下取整、向上取整

function roundNumber(num) { var decimal = num - Math.floor(num); if (decimal >= 0 && decimal <= 0.5) { return Math.floor(num); } else if (decimal > 0.5 && decimal <= 0.9) { return Math.ceil(num); } else { return num; } }

// 测试 console.log(roundNumber(3.2)); // 3 console.log(roundNumber(3.8)); // 4 console.log(roundNumber(3)); // 3