Both for…in and for…of statements iterate over js data structures. The only difference is over what they iterate:
Let’s explain this difference with an example:
1 2 3 4 5 6 7 8 9 10 11 12 13 | let arr = ['a', 'b', 'c']; arr.newProp = 'newVlue'; // key are the property keys for (let key in arr) { console.log(key); } // value are the property values for (let value of arr) { console.log(value); } |
Since for..in loop iterates over the keys of the object, the first loop logs 0, 1, 2 and newProp while iterating over the array object. The for..of loop iterates over the values of a arr data structure and logs a, b, c in the console.
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