There is an
difference b/w the two javascript loop for..in and for..of
Ø
for..in:
The for..in loop
works with array and objects. It
iterates with the property name.
1.1
When
working with array it returns the indexes of the array element and user defined
properties.
eg.
var
arr=[12,13,14,15];
arr.foo='abc';
for (index in
arr)
console.log(index);
// use arr[index] to access the element
Result:
0
1
2
3
foo
1.2
When
working with object it returns the ‘key name’ of the object.
Eg.
var
obj={key1:12,key2:13,key3:14,key4:15};
for (key in obj)
console.log(key);
// use obj[key] to access the element
Result:
key1
key2
key3
key4
Ø
for..of: It works only
with iterable objects. Iterable objects are those object that use Iterable
protocol.
Inbuilt iterable objects
are Array, String, Map, Set, TypedArray. Iterable object have the @@iterator method (i.e Symbol.iterator
key). It iterates with the property value.
Eg.
var
arr=[12,13,14,15];
arr.foo='abc';
for (index of
arr)
console.log(index);
Result:
12
13
14
15
