7个JS基础知识总结

7个JS基础知识总结

作者： 字体：[增加 减小] 类型：转载 时间：2014-03-05 我要评论

这篇文章主要介绍了7个JS基础知识,需要的朋友可以参考下

<iframe id="iframeu2261530_0" src="http://pos.baidu.com/zcmm?sz=680x200&rdid=2261530&dc=2&di=u2261530&dri=0&dis=0&dai=1&ps=390x73&coa=at%3D3%26rsi0%3D680%26rsi1%3D200%26pat%3D6%26tn%3DbaiduCustNativeAD%26rss1%3D%2523FFFFFF%26conBW%3D1%26adp%3D1%26ptt%3D0%26titFF%3D%2525E5%2525BE%2525AE%2525E8%2525BD%2525AF%2525E9%25259B%252585%2525E9%2525BB%252591%26titFS%3D14%26rss2%3D%2523000000%26titSU%3D0%26ptbg%3D90%26piw%3D0%26pih%3D0%26ptp%3D0&dcb=BAIDU_SSP_define&dtm=BAIDU_DUP_SETJSONADSLOT&dvi=0.0&dci=-1&dpt=none&tsr=0&tpr=1461220594608&ti=7%E4%B8%AAJS%E5%9F%BA%E7%A1%80%E7%9F%A5%E8%AF%86%E6%80%BB%E7%BB%93_%E5%9F%BA%E7%A1%80%E7%9F%A5%E8%AF%86_%E8%84%9A%E6%9C%AC%E4%B9%8B%E5%AE%B6&ari=1&dbv=2&drs=1&pcs=1137x582&pss=1137x396&cfv=0&cpl=4&chi=1&cce=true&cec=GBK&tlm=1459262498&ltu=http%3A%2F%2Fwww.jb51.net%2Farticle%2F47699.htm&ltr=https%3A%2F%2Fwww.baidu.com%2Flink%3Furl%3DeLrWvwuZ_F1RTB_aopd6FbDcjkV5qaCm8QXgWU4RBDnYUk0Q_hSmYe8GOCCLUmoq%26wd%3D%26eqid%3D8209cc910000f69000000005571874c1&ecd=1&psr=1366x768&par=1366x728&pis=-1x-1&ccd=24&cja=false&cmi=6&col=zh-CN&cdo=-1&tcn=1461220595&qn=3666b5361563d5ac&tt=1461220594528.85.234.238" width="680" height="200" align="center,center" vspace="0" hspace="0" marginwidth="0" marginheight="0" scrolling="no" frameborder="0" allowtransparency="true" style="display: block; border-width: 0px; border-style: initial; vertical-align: bottom; margin: 0px;"></iframe>

1.如何在一个对象上添加属性？ 

方法一：var b = {};

b["name"] = "test";

delete b.name 删除对象的属性

方法二：b.name ="test";
2.如何判断一个变量是否声明？
typeof(a) =="undefined"

typeof(d) =="function" 是否为函数

3.怎么表示为字符串? 

通过双引号("")，单行号(''),反斜杠(//)

   1+"1"=11

   1+'1'=11
4.Javascript 只有一个数字类型，那就是number.

5.Javascript的基本数据类型？

number(数字),string（字符串）,Boolean（布尔）,undefined（未定义）,Null(空)

另外：Object（对象）

6.类和对象的区别？如何用javascript实现？

复制代码代码如下:

function myClass()

{ }

myClass.prototype.ID = 1;

myClass.prototype.Name = "johnson";

myClass.prototype.showMessage = function()

{

    alert("ID: " + this.ID + "Name: " + this.Name);

}

var obj1 = new myClass();

obj1.showMessage();

7. JavaScript 中，有多少种不同类型的循环？

两种。for 循环和 while 循环。