Return an array of keys from an object [duplicate]

I am pretty new to JavaScript and I am working on this practice question that asks to create a function that returns the keys out of an object (without using the object.keys method). I have tried a few different iterations of the following code, and would appreciate a nudge in the right direction toward solving this problem!

function keys(obj) {
    let firstLoop = [];
    let newObj = Object.entries(obj);
    for (let i = 0; i <= newObj.length; i ++){
        firstLoop.push(newObj[i]);
        return firstLoop;
        
    }
    for (let j = 0; j < firstLoop.length; i ++){
        return firstLoop[j];
    }
}