查找相邻相同字符串

var found = false;


function f(str){
if(found){return;}
var len = str.length;
var a = str.substring(0,len/2);
var b = str.substring(len/2,len);


if(a == b && a!="" && a!=undefined){
console.log("found: " + a+b);
found = true;
return;
}


for(var j = 1;j < len; j++){
for(var i = j%2==0 ? j : j+1;i < len+2; i+=2){
var c = str.substring(j,i);
f(c);
}
}


}


f("abc9habcdefghjabcdefghj");
if(!found){console.log("not found");}