js3:数据类型,数组,String各个属性,以及字符串表达式用eval计算

原文发布时间为:2008-11-08 —— 来源于本人的百度文章 [由搬家工具导入]

<html>
<head>
<title>js</title>

<script type="text/JavaScript">
<!--
var v;
document.write(typeof(v)+"<br>");
v="hello";
document.write("<h1>"+typeof(v)+"</h1>");
v=1;
document.write(typeof(v)+"<br>");
v=1.5;
document.write(typeof(v)+"<br>");
v=2.0e3;
document.write(v+"<br>");
v=true;
document.write(typeof(v)+"<br>");
v=null;
document.write(typeof(v)+"<br>");
var arr=new Array(2);
arr[0]="hi";
arr[1]="2hi";
var arr2=new Array();
arr2[3]="3hi";
for(var i=0;i<arr.length;i++)
document.write(arr[i]+"<br>");
for(var i=0;i<arr2.length;i++)
document.write(arr2[i]+"<br>");
document.write(arr2.length+"<br>");
document.write(arr[0]*5+"<br>");
var num=5;
var str="5";
document.write((num==str)+"<br>");
document.write((num===str)+"<br>");
document.write((num!=str)+"<br>");
document.write((num!==str)+"<br>");
var newstr="JavaScript";
document.write(newstr.fontcolor('red')+"<br>");
document.write(newstr.bold()+"<br>");
document.write(newstr.indexOf("aS",2)+"<br>");
document.write(newstr.indexOf("aS",4)+"<br>");
document.write(newstr.lastIndexOf("aS",3)+"<br>");
document.write(newstr.lastIndexOf("aS",2)+"<br>");
var arrstr=newstr.split('a');
for(var i=0;i<arrstr.length;i++)
document.write(arrstr[i]+" ");

document.write("<br>"+newstr.substring(1,5)+"<br>");
document.write(newstr.toLowerCase()+"<br>");
document.write(newstr.toUpperCase()+"<br>");
var cacu="23"+"*"+"5";
document.write(cacu+"<br>");
document.write(eval(cacu)+"<br>");
//-->
</script>
</head>
<body>
</body>
</html>

运行结果:

undefined

string

number
number
2000
boolean
object
hi
2hi
undefined
undefined
undefined
3hi
4
NaN
true
false
false
true
JavaScript
JavaScript
3
-1
3
-1
J v Script
avaS
javascript
JAVASCRIPT
23*5
115

原文地址:https://www.cnblogs.com/handboy/p/7148412.html