While reviewing code done by a previous developer who is no longer with us, I observed that they sometimes used
Object.assign({}, xyz)
and other times they used
Object.assign([], abc);
Could there be a distinction between the two methods?
While reviewing code done by a previous developer who is no longer with us, I observed that they sometimes used
Object.assign({}, xyz)
and other times they used
Object.assign([], abc);
Could there be a distinction between the two methods?
Indeed, there exists a distinction between the two methods. One method assigns the values to a new object while the other assigns the values to a new array.
Take a look at the displayed results here and compare them with what appears in the actual browser console.
var abc = {foo:"bar"};
var r1 = Object.assign({},abc);
var r2 = Object.assign([],abc);
console.log(r1);
console.log(r2);It's important to note that the second method does not add a new item to the array - it will still have a length of 0.
Object.assign is a method that duplicates the enumerable own properties from one object to another (referred to as the target) and then returns the target object. Even though arrays are considered objects, you can still duplicate properties onto them; however, these properties will not be visible during iteration.
Let's look at this example:
obj is an objectarr is an object, but also an arrayarr.a equals 1arr.forEach does not display aconst obj = Object.assign({}, {
a: 1,
0: 2
});
const arr = Object.assign([], {
a: 1,
0: 2
});
console.log(typeof obj);
console.log(typeof arr);
console.log(Array.isArray(arr));
console.log(obj);
console.log(arr);
console.log(Object.keys(arr));
console.log(arr.a);
arr.forEach((item, idx) => console.log(`${idx}: ${item}`));
// To test the query in the comments
let copiedObj = { a: 123 };
let copy = Object.assign({}, copiedObj);
console.log(copy);
copiedObj = [];
console.log(copiedObj);
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