<p> typeof 操作符返回变量或表达式的类型。</p>

​

<p id="demo"></p>

document.getElementById("demo").innerHTML = 

typeof "john" + "<br>" + 

typeof 3.14 + "<br>" +

typeof false + "<br>" +

typeof [1,2,3,4] + "<br>" +

typeof {name:'john', age:34};