空格转换

将一个字符串中的每个空格替换成“%20”。例如，当字符串为We Are Happy.则经过替换之后的字符串为We%20Are%20Happy

      var test1 = "We Are Happy"; //注意:这三个相邻的字符串，相邻间只有一个空格
      console.log(test1.replace(/s+/g, "%20"));  //输出We%20Are%20Happy
      //可以解决相邻间只有一个空格的情况，但是不符合题意

      //  现在将test改为
      var test2 = "We  Are Happy"; //注意:We和Are之间有2个空格
      console.log(test2.split(" ").join("%20"));  //输出We%20%20Are%20Happy
      //split方法将数组分成了["We","","Are","Happy"];所以每一个空格都能被改为"%20"