Questions about Array.prototype.slice.call and Array.prototype.concat.call

  node.js, question

I want to convert the dom collection obtained through getElementsByTagName into a real array. I am a little confused about the results they produce (different from what I expected). the test code is as follows
http://runjs.cn/code/i517birf

Concat returns the new array only if all the following parameters are arrays (including this), otherwise it is just to form an array of these variables.
Splice wants to delete some items in this, while the return value of getElementByTagName is read-only and cannot be deleted.
http://zonxin.github.io/post/2015/07/javascript-array-prototype