Access element name (no value) from array with javascript

Question

Sorry if my question is bad. I'm stuck in the following simple javascript code:

var person={fname:"John",lname:"Doe",age:25};

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

The above code result is : John Doe 25

How do you show only value from lname element ? (with for (... in ...) statement)

I don't want to use person={"John","Doe",25} instead of one of above. I want to know how to access the element from array to get value.

Thank you

Edit: Thanks all for responses. This question was created because I have many items in array like :

        [{Name="A 1", Email="[email protected]", Group="Group1"},
        {Name="A 2", Email="[email protected]", Group="Group2"},
        {Name="A 3", Email="[email protected]", Group="Group3"},
        {Name="B 1", Email="[email protected]", Group="Group1"},
        {Name="V 1", Email="[email protected]", Group="Group2"},
        {Name="X 1", Email="[email protected]", Group="Group4"},
        {Name="Y 1", Email="[email protected]", Group="Group3"},
        {Name="Z 1", Email="[email protected]", Group="Group3"},
        {Name="W 1", Email="[email protected]", Group="Group6"}]

I want to iterate this array and compare the element with my owned value. if object1.Group == 'Group3' { code }

Do you mean using person.lname? What do you expect the result to be? — David Wolever
– David Wolever, Commented Dec 21, 2011 at 7:28
I want to write lname on the page... for example Doe instead of John Doe 25 — Snake Eyes
– Snake Eyes, Commented Dec 21, 2011 at 7:31

nnnnnn · Accepted Answer · 2011-12-21 08:08:57Z

5

What you have here is not an array, it is a JavaScript object. (In simple terms,) Arrays have numeric indexes, while objects have properties with property-name and value pairs.

To access a specific object property like "lname" simply say:

person.lname
// OR
person["lname"]

Or, if the name of the property you want to use is in a variable:

var whichProp = "lname";
person[whichProp]

With your data, to produce the output "John Doe" you'd say:

document.write(person.fname + " " + person.lname);

The for (x in person) syntax that you were using loops through every property of the person object, setting x to each property name in turn.

UPDATE FOR YOUR UPDATED QUESTION:

Assuming you have an array of objects:

var people = [{Name:"A 1", Email:"[email protected]", Group:"Group1"},
              {Name:"A 2", Email:"[email protected]", Group:"Group2"},
              {Name:"A 3", Email:"[email protected]", Group:"Group3"},
              // etc ];

And you want to find the element where Group is "Group3" then you loop through the array with a traditional for loop as follows:

for (var i=0; i < people.length; i++) {
   if (people[i]["Group"] === "Group3") {
      // do something
   }
}

Within the if statement you can add a break statement if you want to stop processing after the first match. And of course you are free to use the people[i].Group syntax rather than people[i]["Group"] if you prefer it.

(Note also that your object literal syntax was incorrect in your question update: where you've used = you should've used : as shown in my answer above.)

edited Dec 21, 2011 at 8:08

answered Dec 21, 2011 at 7:30

nnnnnn

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3 Comments

Grrbrr404 Over a year ago

Good explanation of all cases. @Michael See my example if you want to have an array of multiple person objects

Snake Eyes Over a year ago

What happens if I want to iterate the big array (see edited code above) and compare element ?

nnnnnn Over a year ago

@MichaelSwan - I've updated my answer to cover your new requirement.

Grrbrr404 · Accepted Answer · 2011-12-21 07:29:17Z

1

var arr = [];
var person={fname:"John",lname:"Doe",age:25};
arr.push(person);

for (var i=0; i < arr.length; i++)
{
   document.write(arr[i].lname+ " ");
}

Update

JsFiddle example

answered Dec 21, 2011 at 7:29

Grrbrr404

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1 Comment

Grrbrr404 Over a year ago

@MichaelSwan could you solve your problem then or is further assistance needed?

Mahmoud Gamal · Accepted Answer · 2011-12-21 07:35:10Z

1

You can access the two properties fname, lname of the person object like this:

document.write(person.fname + " " + person.lname);

edited Dec 21, 2011 at 7:35

answered Dec 21, 2011 at 7:29

Mahmoud Gamal

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1 Comment

Mahmoud Gamal Over a year ago

@MichaelSwan the code above assuming that the person is an array, if it is not an array try it without an index like : person.fname, person.lname see my edit

gilly3 · Accepted Answer · 2011-12-21 08:14:42Z

1

That's not an Array, that's an Object. If you know the property you want to access, you don't need to iterate the Object. Just reference the property directly.

person.lname;

Edit: To iterate your Array and take action when the group matches:

for (var i = 0; i < objects.length; i++) {
    if (objects[i].Group == "Group3") {
        // do something 
    }
}

But, the code you posted is invalid. Property/value pairs are separated with a :, not =.

edited Dec 21, 2011 at 8:14

answered Dec 21, 2011 at 7:31

gilly3

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