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"document.write(sum)" ?? ?? ??? ????? ?? ???.

function add2(x,y)
{
  sum = x + y;   
return sum; //返回函數(shù)值,return后面的值叫做返回值。}

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result = add2(3,4);//語句執(zhí)行后,result變量中的值為7。

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<!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>返回值函數(shù)</title> <script type="text/javascript"> function app2(x,y) { var sum,x,y; sum = x * y; return sum; } var req1 = app2(5,6); var req2 = app2(2,3); var sumq = req1 + req2; document.write("req1的值:"+req1+"<br/>"); document.write("req2的值:"+req2+"<br/>"); document.write(req1+"與"+req2+"和:"+sumq); </script> </head> <body> </body> </html>