Question

121

Pass a string by reference in Javascript

rated 0 times [ 124] [ 3] / answers: 1 / hits: 78179 / 15 Years ago, thu, august 20, 2009, 12:00:00

I want to create a string and pass it by reference such that I can change a single variable and have that propagate to any other object that references it.

Take this example:

function Report(a, b) {

    this.ShowMe = function() { alert(a +  of  + b); }

}



var metric = new String(count);

var a = new Report(metric, a); 

var b = new Report(metric, b); 

var c = new Report(metric, c); 

a.ShowMe();  // outputs:  count of a;

b.ShowMe();  // outputs:  count of b;

c.ShowMe();  // outputs:  count of c;

I want to be able to have this happen:

var metric = new String(count);

var a = new Report(metric, a); 

var b = new Report(metric, b); 

var c = new Report(metric, c); 

a.ShowMe();  // outputs:  count of a;

metric = new String(avg);

b.ShowMe();  // outputs:  avg of b;

c.ShowMe();  // outputs:  avg of c;

Why doesn't this work?

The MDC reference on strings says metric is an object.

I've tried this, which is not what I want, but is very close:

var metric = {toString:function(){ return count;}};

var a = new Report(metric, a); 

var b = new Report(metric, b); 

var c = new Report(metric, c); 

a.ShowMe();  // outputs:  count of a;

metric.toString = function(){ return avg;}; // notice I had to change the function

b.ShowMe();  // outputs:  avg of b;

c.ShowMe();  // outputs:  avg of c;



alert(String(metric).charAt(1)); // notice I had to use the String constructor

// I want to be able to call this: 

// metric.charAt(1)

The important points here:

I want to be able to use metric like it's a normal string object

I want each report to reference the same object.

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

marcos

Add To Favorites

Follow

Total Points: 331

Total Questions: 106

Total Answers: 104

Location: Gabon

Member since Sat, Jul 25, 2020

4 Years ago

marcos questions

1 The above error occurred in the < ArticlePage> component

Thu, Feb 24, 22, 00:00, 2 Years ago

1 how can i setup expiration 30minute in jwt token

Sat, Apr 17, 21, 00:00, 3 Years ago

1 Jest expect exception not working with async

Mon, Feb 1, 21, 00:00, 3 Years ago

1 Need help on a react.js error that I keep on getting

Tue, Jan 26, 21, 00:00, 3 Years ago

1 Axios error: ... .data.pipe is not a function

Wed, Jan 6, 21, 00:00, 3 Years ago

View All

answered 15 Years ago haylie · Accepted Answer

Strings in Javascript are already passed by reference -- calling a procedure with a string does not involve copying the string's contents. There are two issues at hand:

Strings are immutable. In contrast to C++ strings, once a JavaScript string has been created it cannot be modified.

In JavaScript, variables are not statically assigned slots like in C++. In your code, metric is a label which applies to two entirely separate string variables.

Here's one way to achieve what you want, using closures to implement dynamic scoping of metric:

function Report(a, b) {

    this.ShowMe = function() { alert(a() +  of  + b); }

}



var metric = count;

var metric_fnc = function() { return metric; }

var a = new Report(metric_fnc, a); 

var b = new Report(metric_fnc, b); 

a.ShowMe();  // outputs:  count of a;

metric = avg;

b.ShowMe();  // outputs:  avg of b;