txt +=" "和txt = " "区别。待大神！

Question

$("button").click(function(){
var txt=" ";
txt+="Width of div: " + $("#div1").width() + "
";
txt+="Height of div: " + $("#div1").height();
$("#div1").html(txt);
});

Answer 1

var txt=" "; 把字符串给txt
txt+="Width"； 在txt原本的字符串后加上字符串（Width）