for loop - javascript "for (x in y)" statements - Stack Overflow

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//just copied this code from w3schools
var person={fname:"John",lname:"Doe",age:25}; 

for (x in person)
{
document.write(person[x] + " ");
}

I want to know that, what I have to assume instead of "x".

//just copied this code from w3schools
var person={fname:"John",lname:"Doe",age:25}; 

for (x in person)
{
document.write(person[x] + " ");
}

I want to know that, what I have to assume instead of "x".

• javascript
• for-loop
• for-in-loop

Share Improve this question Follow edited Jan 5, 2016 at 11:46 Lucky 17.4k1919 gold badges120120 silver badges156156 bronze badges asked Oct 24, 2011 at 9:39 SiriusKoderSiriusKoder 34122 gold badges44 silver badges1212 bronze badges 6

• Can you specify a little more? What are you trying to achieve? – Jørgen Commented Oct 24, 2011 at 9:43
• Make sure you declare x first... – Matt Commented Oct 24, 2011 at 9:44
• 3 for a better reference look here: developer.mozilla/en/JavaScript/Reference/Statements/… and why so, look here: w3fools. – Yoshi Commented Oct 24, 2011 at 9:45
• Avoid using for in. Use for(var i=0;i<person.length;i++) instead. – OptimusCrime Commented Oct 24, 2011 at 10:24
• 1 Could you explain why? @OptimusCrime – Alexander Mistakidis Commented Dec 11, 2012 at 15:53

 |  Show 1 more ment

2 Answers 2

Sorted by: Reset to default 6

You want to have

for ( x in Object.keys(person)) {
  console.log(person[x]);
}

this will give you a list of KEYS rather than a list of values.

The person is object and X is variable used in iteration of the for loop, you can name it anything other than X also :). Here X works as key of the object for example:

alert(person["fname"]);

Here fname is stored in X along with other keys such as lname and age.

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