js字符串切割，替换函数封装

//字符分割 str.split(通过指定字符分割,返回的最大长度)
var str = split('linfefnglinfeng','n',3); // 1,字符  2指定字符  3.长度（选填）
//console.log(str);
var string = 'linfefnglinfeng';
var m = string.split('n',3);
//console.log(m);
/**
*str　　字符串
*tr　　指定字符
*len　　长度（选填）
*/

function split(str,tr, len=null)
{
        var arr = [];
        var num = str.length;
        var res = 0;
        for(var i =0;i<num;i++){
            var p = i - res;
            if(tr == str[i] || i ==(num-1)){
                if(i == (num-1))p+=1;
                arr.push(str.substr(res,p));
                res = i+1;
            }
            if(arr.length == len)break;
        }
    return arr;
}

//字符替换  replace
var string = "linfenghelloeprd";
console.log(string.replace('ll','&&'));
console.log(replace(string,'ll','&&'));
/**
*str　　字符串
*req　　需要替换的字符
*list　　要替换的值
*/
function replace(str,req,list)
{
    var lenr = req.length;
    var len = str.length;
    var i = 0;
    var data = '';
    for(i;i < len;i++){
        var k = 0;
        var string = '';
        for(k;k < lenr; k++){
            var n = i+k;
            string += str[n];
        }
        if(string == req){
            data += list;
            i = i+lenr;
        }
        data += str[i]
    }
    return data;
}