str:字符串 beginStr:开始位置 endStr:结束位置；
common.desensitization = function(str,beginStr,endStr){
var len = str.length;
var leftStr = str.substring(0,beginStr);
var rightStr = str.substring(endStr,len);
var str = ''
var i = 0;
try {
for (i = 0; i < endStr-beginStr;i++) {
str = str + '*';
}
} catch (error) {
}
str = leftStr + str + rightStr;
return str;
}