Javascript: Object have keys, but Object.keys returns empty

There are 3 factors that can cause the general behavior you describe. In your case, I think it's the first:

1. When you invoke console.log(x), the Chrome console will show a summary of the object x at the time. However, when you expand the object, the value is obtained again. The detailed object you see may have changed since the call to console.log(), and changes will appear in the detail.

2. Properties may belong to an object's prototype (as opposed to "own" properties):

   > x = {a:1}
   { a: 1 }
   > y = Object.create(x)
   > y.a
   1
   > y
   {}
   > Object.keys(y)
   []
   

3. Properties may be non-enumerable, and won't show up in key listings. length is a non-enumerable property.

Try this,

 const keys =[];  
    const person = {
    name : 'Jobelle',
    age :22,
    mob :8547391599
    }
    
    Object.getOwnPropertyNames(tempObj).forEach(prop => {
              keys.push(prop);
            });