非标
此特征是非标准的，且不在标准轨道中。不要在面向 Web 的生产站点中使用它：它不适用于每个用户。实现之间可能存在大的不兼容性，且行为将来可能改变。
Deprecated since Gecko 7.0 (Firefox 7.0 / Thunderbird 7.0 / SeaMonkey 2.4)
This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the
兼容性表格
at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
Returns the size of a file in bytes.
This property is deprecated. Use
Blob.size
代替。
var size = instanceOfFile.fileSize;
A number.
Not part of any specification.
File