RegExp对象的方法

1. pattern.test(str);
返回值是boolean类型，匹配返回true，不匹配返回false
2. pattern.exec(str);
返回值是object类型，匹配返回str对应的字符串，不匹配返回null

var pattern = new RegExp("box","igm");  
var str = "Box";
alert(pattern.test(str));   // true

var pattern = /box/i;
var str = "This is a Box";
alert(pattern.test(str));   // true

var pattern = /box/i;
var str = "Box";
alert(pattern.exec(str));   //Box

var pattern = /box/i;
var str = "aox";
alert(pattern.exec(str));   //null