1)匹配其中一个字符
var t = "1,2,3";
t.replace(",") //"1undefined2,3"
t.replace(",","") //"12,3"
2)匹配其中所有的这个字符
var t = "1,2,3";
t.replace(/,/g,"") //"123"
3)匹配数字,d 查找数字
var t = "分析范围总面积为:6654787.6平方米";
t.replace(/[^d|.]*/g,""); //"6654787.6"