SOURCE

// function foo(p1,p2) {
// 	this.val = p1 + p2;
// }

// // 在这里使用 `null` 是因为在这种场景下我们不关心 `this` 的硬绑定
// // 而且反正它将会被 `new` 调用覆盖掉！
// var bar = foo.bind( null, "p1" );
// bar;
function fool(vertical){
    // const determinedDirection = !!vertical ;
     const determinedDirection = vertical !== null || vertical !== undefined;
     const overflow = determinedDirection?vertical:'getstyle'
     console.log(overflow)
}

<div class="container">

	<div class="index">
		演示环境
		<span>58</span>
    </div>

</div>

.container {
    background-color: red;
}

.index {
    color: white;
    font-size: 20px;
  vertical-align: middle;
}

.index span {
    color: blueviolet;
    font-size: 24px;
    vertical-align: middle;
}