//解析：通過在文檔中調用該方法時，此時文檔流已經關閉，調用該方法是重新開啟輸出資料流進行輸出。
function wr() {
var a = 2;
document.writeln("<script type=text/javascript>");
document.writeln("a=21;","a=30;");
document.writeln("<//script>");
document.writeln("<html><body><table border=1><tr><td>document.write</td></tr></table></body></html>");
document.close();
alert(a);//輸出2
}
//在一個子視窗中進行輸出。
function wr1() {
var document3 = document.frames.myIframe3.document;
var a = 2;
document3.write("<script type=text/javascript>");
document3.write("a=21;","a=30;");
document3.write("<//script>");
document3.write("<html><body><table border=1><tr><td>document.write</td></tr></table></body></html>");
document3.close();
alert(a);//輸出2
}
//解釋：這裡是隨輸出資料流輸出來。//輸出資料流並為關閉，這裡為同一輸出資料流。
var a = 1;
document.write("<script type=text/javascript>");
document.write("a=21;","a=30;");
document.write("<//script>");
document.close();
alert("a-->"+a);//輸出30
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