頭條截到一個面試題，運行了一下，感受到了來自這個世界滿滿的愛。
直接上代碼
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>前端面試題小探（1）</title>
</head>
<body>
<div>
<div>
<p>
var a;<br>
var b = a * 0;<br>
if (b == b) {<br>
console.log(b * 2 + "2" - 0 + 4);<br>
} else {<br>
console.log(!b * 2 + "2" - 0 + 4);<br>
}<br>
</p>
</div>
<button id="first">第一題</button>
<div>
<h3>
涉及知識點
</h3>
<h5>
undifine的任何計算爲NaN
</h5>
<h5>
NaN不等於任何值，包括它本身
</h5>
<h5>
2 + "3" - 2 + 4 => {2+ "" + (3-2+4)}
</h5>
<h5>
2 + "3" + 4 - 2 => {2+ "3" + "" + (4-2)}
</h5> </div></div><script type="text/javascript" src="../jquery/jquery-min.js"></script><script type="text/javascript"> $("#first").click(function() { var a; var b = a * 0; var c = a - 3; console.log(a,"aaa"); console.log(b,"bbb"); console.log(c,"ccc"); console.log(NaN*2,"nan*2"); console.log(!b,"!b"); console.log("2" - 0); console.log(!b * 2); console.log("23" + 2 + 10,"\"23\" + 2 + 10"); console.log(!b * 2 + "2" + 4); console.log( 2 + "3" + 4); console.log( 2 + "3" - 2 + 4,"2 + \"3\" - 2 + 4"); console.log( 2 + "3" + 4 - 2,"2 + \"3\" + 4 - 2"); console.log("3" - 2); console.log("3" + 2); if (b == b) { console.log(b * 2 + "2" - 0 + 4); } else { console.log(!b * 2 + "2" - 0 + 4); } var getType=Object.prototype.toString; console.log(getType.call(a)) console.log(getType.call(b)) console.log(getType.call(c)) console.log(getType.call(NaN*2)) console.log(getType.call(!b),"!b") console.log(getType.call(!b * 2),"!b * 2") console.log(getType.call("5" - 2),"\"5\" - 2") console.log(getType.call("5" + 2),"\"5\" + 2") console.log(getType.call(2 - "3")) console.log(getType.call("2")) console.log(getType.call("23" + 2 + 10)) console.log(getType.call( "2" - 0 + 4)," \"2\" - 0 + 4",( "2" - 0 + 4)); console.log(getType.call(!b * 2 + "2" - 0 + 4),"!b * 2 + \"2\" - 0 + 4",(!b * 2 + "2" - 0 + 4)) })</script></body></html>
小菜鳥的console.log幫手，運行結果打印
