编写一个 function 称为键，它接受 object 并返回 object 中所有键的数组

Question

Beginner at JavaScript. I can't use the Object.keys() function. This is what I have so far. I can't for the life of me figure out how to return all the keys in the object, it's only returning "['a']", the first key:

const keys = (obj) => {
var obj1 = {a: 1, b: 2, c: 3};
var newArray = [];

for(var key in obj1) {
  newArray.push(key);
  return newArray;
}

};

keys();

Answer 1

Your loop will only run once because your return statement is inside the loop, which terminates your entire function, including the loop.

Madhawa Priyashantha is right: put the return statement after the loop and it should work.

Answer 2

The return statement inside the for loop terminates it after the first iteration so you should put the return statement after the loop as shown below.

 const keys = (obj) => { var obj1 = { a: 1, b: 2, c: 3 }; var newArray = []; for (var key in obj1) { newArray.push(key); } return newArray; }; keys();

Answer 3

Facetiously not using Object.keys() - you can use Object.entries() and map() and to create an array of the first item in the key: value pairings.

Presumably this is some sort of homework or teaching activity - the reason for my post is to show that there are many ways to achieve the outcome and some are just different ways of saying the same thing.

The obvious answer is to use a loop as per your attempt and the other solutions - but my solution is intended to invite you to see things in a different way. And putting arbitary limits on the way you can achieve something forces you to adopt either inefficient proactise or prevents you from using newer methodologies.

Rather than forcing you to use a loop - a better teaching activity would be to get you to use the newer javascript methods- especially map(), reduce() and filter().

There are definitely reasons to get you to learn loops - but doing so in an exercise to get the keys of an object limits your ability to use current code approaches and is just wrong. IMO.

FYI - I am an ex-teacher and believe in using the right learning activity and the right learning tools to achieve the learning.

 const keys = (obj) => { return Object.entries(obj).map(item => item[0]); }; const obj = {a: 1, b: 2, c: 3}; console.log(keys(obj)); // gives ["a", "b", "c"]