javascript - Why Buffer copy prints me some garbage value? -

i new node.js,

i reading on node.js buffers.

i stumbled on buffer.copy method.

wrote code follows,

var bufferone = new buffer("this china"); var buffertwo = new buffer(20),    starttarget = 0,    sourcestart = 8,    sourceend = 0; var bufferlength = bufferone.length; sourceend = bufferlength; console.log("buffer length "+bufferlength); bufferone.copy(buffertwo,starttarget,sourcestart,sourceend);  console.log("buffer1 "+bufferone.tostring());    console.log("buffer2 "+buffertwo.tostring()); 

the output follows,

buffer length 13 buffer1 china buffer2 china 

but prints garbage output after "china", follows,

buffer length 13 buffer1 china buffer2 china���*� 

sometimes,

buffer length 13 buffer1 china buffer2 china��� 

can please tell me whats going on ?

the length of buffertwo 20, you're copying 13 bytes. remaining 7 bytes contain semi-random data.

documented here:

passing number first argument buffer() (e.g. new buffer(10)), allocates new buffer object of specified size. memory allocated such buffer instances not initialized , can contain sensitive data.