title: node.js convert binary string to number
body: <p>Writing a node.js application, it receives from a socket a binary string of 4 bytes "\x00\x00\x00\x13", I need to convert it to integer (19 which is 0x13 in our case) using big endian order.</p>
  
  <p>In other scripting languages, like perl, we can do unpack.
      unpack("N", )</p>
  
  <p>In node.js, not sure how do do it.</p>