我如何警报（）； 这个JS函数的结果？

Question

I am doing the following exercise (while studying JS):

"Create a function multiplyNumeric(obj) that multiplies all numeric properties of obj by 2."

The solution is:

function multiplyNumeric(obj) {
  for (let key in obj) {
    if (typeof obj[key] == 'number') {
      obj[key] *= 2;
    }
  }
}

multiplyNumeric does not need to return anything, it should modify the object in-place.

But what if I want to alert it? I tried different solutions, but I can't get it right..is there a reason why it doesn't alert or I'm just doing it wrong? (exercise reference here: https://javascript.info/object )

I tried:

    let obj = {
    first: 100,
    second: 200,
    third: "Hello"
    };

    function multiplyNumeric(obj) {
      for (let key in obj) {
        if (typeof obj[key] == 'number') {
         obj[key] *= 2;
        } 
      }
    }

 alert(obj); 

In this case it alerts: [object Object]

I also tried alert(obj.first); but it alerts 100. I tried to put the alert(obj); inside the curly braces but it does nothing.

Please be patient, I am just a beginner...

Answer 1

Consider using console.log() as it will display objects nicely. However if you are determined to use alert() you should know that alert() only takes in strings. So try alert(JSON.stringify(obj))

Answer 2

to alert each key in obj seperatly:

function multiplyNumeric(obj) {
      for (let key in obj) {
        if (typeof obj[key] == 'number') {
          obj[key] *= 2;
          alert(obj[key]);
        }
      }
    }

if you want to alert it together, after all the multiply finish, than

function multiplyNumeric(obj) {
      for (let key in obj) {
        if (typeof obj[key] == 'number') {
          obj[key] *= 2;
        }
      }
      alert(JSON.stringify(obj));
    }

Answer 3

Use console.log() let obj = { first: 100, second: 200, third: "Hello" };

function multiplyNumeric(obj) {
  for (let key in obj) {
    if (typeof obj[key] == 'number') {
     obj[key] *= 2;
    } 
  }
}

Console.log(obj);

Answer 4

I don't see any alert() in the question. Since, I don't have much reputation to comment, I am writing the code which works.

function multiplyNumeric(obj) {
  for (let key in obj) {
    if (typeof obj[key] == 'number') {
      obj[key] *= 2;
    }
  }
}
var obj = {'number' : 2};
multiplyNumeric(obj);
alert(obj['number']);