Edit in JSFiddle

<p id="withoutArgument"></p>
<p id="emptyString"></p>
<p id="withPlus"></p>
<p id="withUnderscore"></p>

var myArray = ["one", "two", "three", "four", "five"];

$("#withoutArgument").html("<b>Without Argument : </b>" + myArray.join());
$("#emptyString").html("<b>Empty String : </b>" + myArray.join(" "));
$("#withPlus").html("<b>With plus : </b>" + myArray.join(" + "));
$("#withUnderscore").html("<b>With Underscore : </b>" + myArray.join(" _ "));