18

okay so I have this code in body:

<input type="text" value="haha" id="full_name"/>

And this code in script

<script language="javascript" type="text/javascript">
    function first(){
        var nameContent=document.getElementById('full_name').value;
    }

    function second() {
        first();
        y=nameContent; 
        alert(y);
    }
    second();
</script>

I want a alert showing the value of the element full_name, but it doesn't seem to work, does anyone know why? :S

The Alpha
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Maria
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5 Answers5

20

nameContent only exists within the first() function, as you defined it within the first() function.

To make its scope broader, define it outside of the functions:

var nameContent;

function first(){
    nameContent=document.getElementById('full_name').value;
}

function second() {
    first();
    y=nameContent; alert(y);
}
second();

A slightly better approach would be to return the value, as global variables get messy very quickly:

function getFullName() {
  return document.getElementById('full_name').value;
}

function doStuff() {
  var name = getFullName();

  alert(name);
}

doStuff();
Blender
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  • I think using a global var the **same** as using a function to return it's value, both are global scope, isn't? One problem regarding your approach is that always when getFullName() is called, a DOM search will be done, if a var were used, that DOM search would be called just once. – Marcelo Assis Aug 05 '12 at 04:03
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    No, they're quite different because global variables that hold static values aren't functions. As for the searching, isn't that the point? You want to get the current value of the element with the id of `full_name`. If that value was static, it would be pointless to have a function return the static variable. – Blender Aug 05 '12 at 04:08
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    What I really want to say that it can be optimized. You can hold the DOM object in a var: `nameElement = document.getElementById('full_name');` and whenever needs it's value, use `nameElement.value`. – Marcelo Assis Aug 05 '12 at 04:13
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    The performance boost is absolutely tiny. At 2 million calls/second, I doubt you will notice any speed differences: http://jsperf.com/getelementbyid1232 – Blender Aug 05 '12 at 04:34
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    Sure it is, in this test, but if you think of a big page with lots of elements, running on a PC with low performance, with lots of open tabs in a Firefox, with lots of add-ons... – Marcelo Assis Aug 05 '12 at 17:59
4

Your nameContent scope is only inside first function. You'll never get it's value that way.

var nameContent; // now it's global!
function first(){
    nameContent = document.getElementById('full_name').value;
}

function second() {
    first(); 
    y=nameContent; 
    alert(y);
}
second();
Marcelo Assis
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1

you need a return statement in your first function.

function first(){
    var nameContent = document.getElementById('full_name').value;
    return nameContent;
}

and then in your second function can be:

function second(){
    alert(first());
}
Jason Fingar
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1

Your nameContent variable is inside the function scope and not visible outside that function so if you want to use the nameContent outside of the function then declare it global inside the <script> tag and use inside functions without the var keyword as follows

<script language="javascript" type="text/javascript">
    var nameContent; // In the global scope
    function first(){
        nameContent=document.getElementById('full_name').value;
    }

    function second() {
        first();
        y=nameContent; 
        alert(y);
    }
    second();
</script>
The Alpha
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0

the OOP way to do this in ES5 is to make that variable into a property using the this keyword.

function first(){
    this.nameContent=document.getElementById('full_name').value;
}

function second() {
    y=new first();
    alert(y.nameContent);
}
Ricardo Mendoza
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