字符串操作——插入、替换、删除

//提取查找字符串前面所有的字符
function getFront(mainStr,searchStr){
foundOffset=mainStr.indexOf(searchStr);
if(foundOffset==-1){
return null;
}
return mainStr.substring(0,foundOffset);
}
//提取查找字符串后面的所有字符
function getEnd(mainStr,searchStr){
foundOffset=mainStr.indexOf(searchStr);
if(foundOffset==-1){
return null;
}
return mainStr.substring(foundOffset+searchStr.length,mainStr.length);
}
//在字符串 searchStr 前面插入字符串 insertStr
function insertString(mainStr,searchStr,insertStr){
var front=getFront(mainStr,searchStr);
var end=getEnd(mainStr,searchStr);
if(front!=null && end!=null){
return front+insertStr+searchStr+end;
}
return null;
}
//删除字符串 deleteStr
function deleteString(mainStr,deleteStr){
return replaceString(mainStr,deleteStr,"");
}
//将字符串 searchStr 修改为 replaceStr
function replaceString(mainStr,searchStr,replaceStr){
var front=getFront(mainStr,searchStr);
var end=getEnd(mainStr,searchStr);
if(front!=null && end!=null){
return front+replaceStr+end;
}
return null;
}