4.5 格式化IF语句

文章标题：Learn JavaScript: Lesson 4: Decision Making (part two)
作者：Stephen Chapman
译者：郝晓茹
原文地址：
http://javascript.about.com/od/decisionmaking/a/des07.htm
http://javascript.about.com/library/bldes08.htm
http://javascript.about.com/od/decisionmaking/a/des09.htm
http://javascript.about.com/od/decisionmaking/a/des10.htm
http://javascript.about.com/od/decisionmaking/a/des11.htm
http://javascript.about.com/od/decisionmaking/a/des12.htm
http://javascript.about.com/od/decisionmaking/a/des13.htm