JS的parent对象
https://blog.csdn.net/xing_1209/article/details/114664315?utm_medium=distribute.wap_aggpage_search_result.none-task-blog-2aggregatepagefirst_rank_ecpm_v1~rank_v31_ecpm-1-114664315.wap_agg_so&utm_term=js%E4%B8%AD%E7%9A%84parent%E5%AF%B9%E8%B1%A1
Window对象、Parent对象、Frame对象、Document对象和Form对象的阶层关系:Windwo对象→Parent对象→Frame对象→Document对象→Form对象,
如下:parent.frame1.document.forms[0].elements[0].value;
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