var str = "aaabbbcccdddeee000";
str = str.match(/(\S*)000/)[1];
alert(str);//结果aaabbbcccddd
var str = "000bbbcccdddeeefff";
str = str.match(/000(\S*)/)[1];
alert(str);//结果bbbcccdddeeefff
var str = "123abcdefg456";
str = str.match(/123(\S*)456/)[1];
alert(str);//结果abcdefg