1. Object reference
In JS, var a = [1,2];var b=a; b.splice(0,1); I thought that the first item in array b would be deleted, but it turned out that the first item of data in a was also deleted ;
var a = [1,2,3];
var b = a;
b.splice(1,1);
console.log(b) //[1,3]
console.log(a) //[1,3]
I checked that this is caused by the pointer of the object pointing to the same place, but at present it can only be checked like this: var b = JSON.parse(JSON.stringfy(a)); The pointer can be changed by assignment conversion;
Just checked the draft box, you need to look at the JS data type
2. CSS vertical centering
What I knew before was display: flex; + align-items: center;
But after checking, it seems that there are some other convenient css https://www.zhihu.com/question/20543196