用for优化js代码怎样实现

Question

f1x - f4x是动态添加的，数量可能多也可能少

var f1x = document.getElementById("f1x").value;
var f2x = document.getElementById("f2x").value;
var f3x = document.getElementById("f3x").value;
var f4x = document.getElementById("f4x").value;
...

document.getElementById("fxx").value=f1x+f2x+f3x+f4x+...;

以上用for怎样才能实现

Answer 1

for (var i = 1; i <=4; i++)
document.getElementById("fxx").value = document.getElementById("fxx").value + document.getElementById("f" + i + "x").value;