javascript的数据类型

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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title></head><body><h1>javascript的字符串</h1><script>var carname1 = "双引号";var carname2 = '单引号';var answer1 = "双引号";var answer2 = "双引号中的'单引号'";var answer3 = '单引号中的"双引号"';document.write(carname1 + "<br />");document.write(carname2 + "<br />");document.write(answer1 + "<br />");document.write(answer2 + "<br />");document.write(answer3 + "<br />");</script><br />··················································································<br /><h1>javascript 数字</h1><script>var a = 36.00;var b = 36var c = 123e5;var d = 123e-5;document.write(a + "<br>");document.write(b + "<br>");document.write(c + "<br>");document.write(d + "<br>");</script><br />···················································································<br />JavaScript 布尔布尔（逻辑）只能有两个值：true 或 false。var x=truevar y=false布尔常用在条件测试中。<br />···················································································<br /><h1>javascript 数组</h1><script>var i;var cars = new Array();cars[0] = "123";cars[1] = '456';cars[2] = '789';for(i=0;i<cars.length;i++){document.write(cars[i] + "<br>");}</script><br />···················································································<br /><h1>javascript 对象</h1><p>对象由花括号分隔。在括号内部，对象的属性以名称和值对的形式 (name : value) 来定义。属性由逗号分隔</p><script>var person={varname1 : "123",varname2 : "456",varname3 : "789"}//对象属性有两种寻址方式：document.write(person.varname1 + "<br>");document.write(person["varname2"] + "<br>"); </script><br />···················································································<br /><h1>Undefined 和 Null</h1><script>var name1;var name2 = "hallo";document.write(name1 + "<br>");//Undefined 这个值表示变量不含有值。document.write(name2 + "<br>")var name2 = null;//可以通过将变量的值设置为 null 来清空变量。var name1 = null;document.write(name1 + "<br>");document.write(name2);</script><br />···················································································<br /><h1>声明变量类型</h1>当您声明新变量时，可以使用关键词 "new" 来声明其类型：<br />var carname=new String;<br />var x=      new Number;<br />var y=      new Boolean;<br />var cars=   new Array;<br />var person= new Object;<br />JavaScript 变量均为对象。当您声明一个变量时，就创建了一个新的对象。<br /></body></html>
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