How to pass a string value as a reference in javascript and change it over there.

Question

How can I pass a string value by reference in javascript.

I want this kind of functionality.

    //Library.js
    function TryAppend(strMain,value)
    {
    strMain=strMain+value;
    return true;
    }

    //pager.aspx

    function validate()
    {
    str="Checking";
    TryAppend(str,"TextBox");
    alert(str); //expected result "Checking" TextBox
    //result being obtained "Checking"    
    }

How to do this. ?

Answer 1

You cannot pass a value by reference in JS. You could create an object with a function to do this for you:

function TryAppend(originalValue) {

    // Holds the value to return
    this.Value = originalValue;

    // The function joins the two strings
    this.Append = function (append) { 
        this.Value+=append; 
        return true;
    }

}

You can then use this in any method as follows:

function AnyProcedure() {

    var str = "Checking";
    var append = new TryAppend(str);
    if (append.Append("TextBox")) {
        alert(append.Value);  // Will give "CheckingTextBox"
    }

}

Each time you call append, the Value string will be appended to. I.e.

If you then did:

append.Append(" Foo");

append.Value would equal CheckingTextBox Foo.

Answer 2

You need to return the String instead of true !!

    function TryAppend(strMain,value)  { 

    strMain=strMain+value; 

    return strMain; //you need return the  'String Value' to use in it another method

    } 


    //pager.aspx 


    function validate() { 

    str="Checking"; 

    str = TryAppend(str,"TextBox"); 

    alert(str); //expected result "Checking" TextBox 

    //result being obtained "Checking"     
    } 

Answer 3

Create a global variable (say gblstrMain) outside the function TryAppend and then set its value to strMain inside the function.

    var gblstrMain;

function TryAppend(strMain,value)
    {
    strMain=strMain+value;
    gblstrMain = strMain;
    return true;
    }

    //pager.aspx

    function validate()
    {
    str="Checking";
    TryAppend(str,"TextBox");
    str = gblstrMain;
    alert(str); //expected result "Checking" TextBox
    //result being obtained "Checking"    
    }

Since you are particular about "return true" in the TryAppend function, we can achieve by this workaround.