Is there a toString-like function for javascript objects?

Question

While debugging and developing with javascript, I often wanted to alert the objects, so I used the below code:

for(a in obj)
{
  alert(a +' = '+obj[a])
}

It serves well, but it is too annoying. I want to know if there is anything just like this for arrays:

var temp = ['a','b','c'];
alert(temp); // it will alert a,b,c

So what I wish to do is:

var temp = {a:'a',b:'b',c:'c'};
alert(temp) ; // It should alert json {a:'a',b:'b',c:'c'}

Or any other better suggestion so I could look up the object easily.

@JamesAllardice yes it is good one but I want to extend the object definition. How it has been done in case of array that they are alerted like strings ? — Rupesh Patel, Jul 24 '12 at 13:49
@RupeshPatel - The way it's done with arrays is an internal part of the language. It's documented in detail in the ECMAScript specification. The same is not true of objects. You can overwrite the `Object.prototype.toString` method, or you can call another function as shown in various answers. — James Allardice, Jul 24 '12 at 13:52

score 4 · Accepted Answer · answered Jul 24 '12 at 13:49

4

Alert calls toString, so you can overwrite toString for debugging purposes:

Object.prototype.toString = function() {
    return JSON.stringify(this);
};

So you can just call alert(foo); and it will display the JSON representation of foo

answered Jul 24 '12 at 13:49

Ortiga

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Oh my my how I have ignored this thing. Thanks any way :) – Rupesh Patel Jul 24 '12 at 13:54
And hopefully in your code base someone is not doing bad object detection and you break it be overriding toString globally. – epascarello Jul 24 '12 at 14:38
@epascarello for me it is just for debugging purpose commenting two lines after finishing wont any matter. thanks for the comment. – Rupesh Patel Jul 24 '12 at 17:40

score 3 · Answer 2 · answered Jul 24 '12 at 13:42

3

Use

alert(JSON.stringify(temp)) ;

instead of

alert(temp) ;

answered Jul 24 '12 at 13:42

bugwheels94

30,681
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yes it is good one but can I make some thing just like array so alert(temp) can work. so all the objects can share the method whenever they are alerted. – Rupesh Patel Jul 24 '12 at 13:46

score 1 · Answer 3 · answered Jul 26 '12 at 17:08

1

You can also do this so the alerted format can be as you want

 Object.prototype.toString = function{
    var str='';
    for(a in this)
    {
      str+=a +' = '+obj[a]);
    }    
    }

answered Jul 26 '12 at 17:08

RVPatel

41
3

it is also a good suggestions I guess I should go this way thanks:) – Rupesh Patel Jul 26 '12 at 17:10

john2o01 · Answer 4 · 2012-07-24T14:04:34.603

0

The javascript reference guide says there is a toString method for javascript Objects, see the page https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/toString

It is on the mozilla developer page but I believe that should be what you need. excerpt is here, " var o = new Object(); o.toString(); "

edited Jul 24 '12 at 14:04

answered Jul 24 '12 at 13:41

john2o01

61
8

The question is asking about objects, not arrays. – James Allardice Jul 24 '12 at 13:42
sorry I understand what you meant now the line, "I want to know if there is anything just like for arrays" confused me. Sorry – john2o01 Jul 24 '12 at 14:01
edited for what I found. there are a few other methods to go along with those, "https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object" this page has them – john2o01 Jul 24 '12 at 14:06

score 0 · Answer 5 · edited May 23 '17 at 10:29

One solution is:

dump() - Javascript equivalent of PHP's print_r() function

Perl provides Data::Dumper for work like this. Perfect for situations like this. Great for debugging.

A better approach is using JSON.stringify:

JSON.stringify({a:1,b:2,c:{d:1,e:[1,2]}}, null, 4); // Indented 4 spaces
JSON.stringify({a:1,b:2,c:{d:1,e:[1,2]}}, null, "\t"); // Indented with tab

Ref: How Can I Beautify JSON Programmatically

And alert() will only cause you more grief, start using console log. They are persistent and allows you to refer to the output more consistently.

Ref: How to Print Debug Messages in the google chrome javascript console

Better yet: Use a JavaScript debugger to analyse your objects. This is generally a better experience than simply printing or alertingthings out. But console logs are generally better if you have to do this in many locations.

Ref: How do you launch the javascript debugger in Google Chrome?

score 0 · Answer 6 · answered Jul 24 '12 at 13:44

0

Or any other better suggestion so I could look up the object easily.

Most good browsers' console will let you drill down into an object if you log it. For example, with Chrome:

console.log(obj);

Will log a tree-view object to the console.

answered Jul 24 '12 at 13:44

Rob Hruska

118,520
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score 0 · Answer 7 · edited Sep 07 '12 at 18:26

you can use this function:

function dump(arr,level) {
    var dumped_text = "";

    if(!level) level = 0;
    var level_padding = "";

    for(var j=0;j<level+1;j++)
        level_padding += "    ";

    var type = typeof(arr);

    if (arr === null){
        dumped_text = "null";
    } else if (arr instanceof Array) {
        dumped_text += "[";

        for(var item in arr) {
            var value = arr[item];
            dumped_text += dump (value, level+1) + ',';
        }

        if(dumped_text.length > 1)
            dumped_text = dumped_text.substring (0, dumped_text.length-1);
        dumped_text += "]";
    } else if(type == 'object') {
        dumped_text += "{\n";

        for(var item in arr) {
            var value = arr[item];
            dumped_text += level_padding + item + " : ";
            dumped_text += dump(value,level+1) + ',\n';
        }

        if(dumped_text.length > 2)
            dumped_text = dumped_text.substring (0, dumped_text.length-2);

        dumped_text += "\n" + level_padding.substring (0, level_padding.length-4) + "}";
    } else if (type == 'string'){
        dumped_text = "'" + arr + "'";
    } else if (type == 'number'){
        dumped_text = arr + "";
    } else if (type == 'boolean'){
        dumped_text = arr + "";
    }
 return dumped_text;
}

Is there a toString-like function for javascript objects?

7 Answers7