how to declare a global variable assign value in one function and use in another function in javascript

Question

I just write a test html file to learn about object in javascript. The code is as follows

in script tag

<script type="text/javascript">

    var obj = new ParentFn();
    var obj2 = new AnotherParentFn();
    var temp;
    function initer()
    {
        temp = obj.Adding();
        obj2.caller();
    }
    function ParentFn()
    {
        this.a = 10;
        this.b = 20;
    }
    function AnotherParentFn()
    {
        this.a = 30;
        this.b = 50;
    }
    AnotherParentFn.prototype.caller = function()
    {
        var self = this;
        temp();
    }
    ParentFn.prototype.Adding = function()
    {
        var self = this;
        document.getElementById("id_div1").innerHTML = " Method Called and Result of a+b is " + (self.a + self.b);          
    }

</script>

In body i use

<button onclick="initer()"> Click here to test </button>
<div id="id_div1"></div>

Problem is when AnotherParentFn.prototype.caller is called from initer() function temp variable is still undefined. What is wrong with the code??

My task is to assign the function ParentFn.prototype.Adding in a global variable and call the global variable from AnotherParentFn.prototype.caller function. How to achieve it?

Your temp variable is already global now

Prasath K
– Prasath K

2013-04-02 05:59:26 +00:00
Commented Apr 2, 2013 at 5:59 — Prasath K
– Prasath K, Commented Apr 2, 2013 at 5:59
Would be great if you could accept any of the answers.

hifier
– hifier

2013-04-06 04:22:40 +00:00
Commented Apr 6, 2013 at 4:22 — hifier
– hifier, Commented Apr 6, 2013 at 4:22

hifier · Accepted Answer · 2013-04-02 06:19:21Z

1

You don't need to save it as a global variable. It's already saved in ParentFn.prototype. All you need to do is invoke it with .call and pass in your desired receiver. You can implement AnotherParentFn.prototype.caller like this:

AnotherParentFn.prototype.caller = function()
{
    ParentFn.prototype.Adding.call(this);
}

This way you can get rid of temp completely. You also don't need to assign this to a local var self everywhere.

answered Apr 2, 2013 at 6:19

hifier

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Comments

gilly3 · Accepted Answer · 2013-04-02 06:03:29Z

0

Parentheses are used to execute a function. When you assign the value to temp, you are calling the function and assigning the result (undefined) to temp. To store a reference to the function in temp, omit the parentheses.

temp = obj.Adding;

answered Apr 2, 2013 at 6:03

gilly3

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Comments

999k · Accepted Answer · 2013-04-02 06:03:00Z

0

By writing temp = obj.Adding(); it stores the return value. not function pointer in temp. Use this

function initer()
{
    temp = obj.Adding;
    obj2.caller();
}

answered Apr 2, 2013 at 6:03

999k

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Comments

Ja͢ck · Accepted Answer · 2013-04-02 06:10:14Z

0

First of all, the reference to obj.Adding is not assigned properly; it should be this (without parentheses):

function initer()
{
    temp = obj.Adding;
    obj2.caller();
}

Then, inside AnotherParentFn.prototype.caller itself, you must pass the current object as this explicitly during the invocation by using .call():

AnotherParentFn.prototype.caller = function()
{
    temp.call(this);
}

answered Apr 2, 2013 at 6:10

Ja͢ck

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