Automatically updating the actual parameters in javascript

Question

How to pass a primitive variable (like a string) by reference when calling a java script method? Which is equivalent of out or ref keyword in C#.

I have a variable like var str = "this is a string"; and passing the str into my function and automatically have to reflect the change in str when i change the argument value

function myFunction(arg){
    // automatically have to reflect the change in str when i change the arg value
    arg = "This is new string";
    // Expected value of str is "This is new string"
}

Possible duplicate of stackoverflow.com/questions/373157/… — Dan Lister
– Dan Lister, Commented Jun 14, 2012 at 15:15
check this out: snook.ca/archives/javascript/javascript_pass — kol
– kol, Commented Jun 14, 2012 at 15:16
possible duplicate of Pass a string by reference in Javascript — Felix Kling
– Felix Kling, Commented Jun 14, 2012 at 15:17
Possible duplicate of stackoverflow.com/questions/2423868/… alemjerus's answer to that is probably what you want. Convert it to an object. — sachleen
– sachleen, Commented Jun 14, 2012 at 15:17
@Dan, this doesn't seem to be a duplicate of that function. Here, the OP simply wants to know the best way to pass a function argument by reference in JS; the referenced question deals with references to a function object itself. — apsillers
– apsillers, Commented Jun 14, 2012 at 15:20

Angel · Accepted Answer · 2012-06-14 15:40:53Z

3

Primitive types, that is strings/numbers/booleans are passed by value. Objects such as functions, objects, arrays are "passed" by reference.

So, what you want won't be possible, but the following will work:

        var myObj = {};
        myObj.str = "this is a string";
        function myFunction(obj){
            // automatically have to reflect the change in str when i change the arg value
            obj.str = "This is new string";
            // Expected value of str is "This is new string"
        }
        myFunction(myObj);
        console.log(myObj.str);

edited Jun 14, 2012 at 15:40

answered Jun 14, 2012 at 15:31

Angel

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2 Comments

josh3736 Over a year ago

This is mostly true, but pedants will tell you that JavaScript is pure pass-by-value, and the value passed for objects is itself a reference. However, this is confusing, and from a practical standpoint, it basically looks like objects are passed by reference.

Angel Over a year ago

Well, yes, that is what I actually wanted to say.

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