var a = 1 if (a>2){ console.log('该数智太大了'); } else if (a===1){ console.log('该数值正好'); } else{ console.log('该数值小了'); } var non = NaN var a = 0.0000001 var b = Math.abs(2/3) if (a<b){ console.log(isNaN(non)) } console.log(b)