var str = 'I LOVE YOU';
    //加密btoa
    var jiaMi = btoa(str);
    alert(jiaMi) ; //結果為SSBMT1ZFIFlPVQ==
    //加密 atob
    var jieMi = atob(jiaMi);
    alert(jieMi)

 var str = 'i love中國';
    //加密encodeURIcomponent
    var jiaMi = encodeURIComponent(str);
    alert(jiaMi) ; //結果為i%20love%E4%B8%AD%E5%9B%BD ，你會發現英文字母沒有加密
    var jiaM = btoa(jiaMi);
    alert(jiaM) ; //結果為aSUyMGxvdmUlRTQlQjglQUQlRTUlOUIlQkQ=

    //解密，先用atob解密ascii碼，然后再用decodeURIComponent
    var jieMi = atob(jiaM);
    var jieM = decodeURIComponent(jieMi);
    alert(jieM)