var list = [{'a': 1},{'a': 2}];
var newList = list.map(function(index){
return index.a += 1;
});
console.log(newList,'newList',list,'list');
// list也改變了 list = [{'a': 2},{'a': 3}]
// 本人小白，求大神指教，勿噴，謝謝！
2
0
0
It has nothing to do with map
js objects are reference types, characters and numbers are basic types
Basic type value transfer is copying
Reference type passing by value is a reference
For example:
var a = 1;
var b = a;
b++;
console.log(a);
and
var a = [1];
var b = a;
b[0]++;
console.log(a);You first modify a single key value of the list, and then return the key value, naturally modifying two!
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