How do I display the content of a JavaScript object in a string format like when we alert
a variable?
The same formatted way I want to display an object.
How do I display the content of a JavaScript object in a string format like when we alert
a variable?
The same formatted way I want to display an object.
Use native JSON.stringify
method.
Works with nested objects and all major browsers support this method.
str = JSON.stringify(obj);
str = JSON.stringify(obj, null, 4); // (Optional) beautiful indented output.
console.log(str); // Logs output to dev tools console.
alert(str); // Displays output using window.alert()
Link to Mozilla API Reference and other examples.
obj = JSON.parse(str); // Reverses above operation (Just in case if needed.)
Use a custom JSON.stringify replacer if you encounter this Javascript error
"Uncaught TypeError: Converting circular structure to JSON"
HTML tag. For benefiting from the improved indenting of this stringified JSON, wrap that string instead.– Koolstr Oct 15 '20 at 14:20
If you want to print the object for debugging purposes, use the code:
var obj = {
prop1: 'prop1Value',
prop2: 'prop2Value',
child: {
childProp1: 'childProp1Value',
},
}
console.log(obj)
will display:
Note: you must only log the object. For example, this won't work:
console.log('My object : ' + obj)
Note ': You can also use a comma in the log
method, then the first line of the output will be the string and after that, the object will be rendered:
console.log('My object: ', obj);
var output = '';
for (var property in object) {
output += property + ': ' + object[property]+'; ';
}
alert(output);
console.dir(object)
:
Displays an interactive listing of the properties of a specified JavaScript object. This listing lets you use disclosure triangles to examine the contents of child objects.
Note that the console.dir()
feature is non-standard. See MDN Web Docs
console.log(JSON.stringify(obj))
This will print the stringify version of object. So instead of [object]
as an output you will get the content of object.
Well, Firefox (thanks to @Bojangles for detailed information) has Object.toSource()
method which prints objects as JSON and function(){}
.
That's enough for most debugging purposes, I guess.
If you want to use alert, to print your object, you can do this:
alert("myObject is " + myObject.toSource());
It should print each property and its corresponding value in string format.
If you would like to see data in tabular format you can use:
console.table(obj);
Table can be sorted if you click on the table column.
You can also select what columns to show:
console.table(obj, ['firstName', 'lastName']);
You can find more information about console.table here
Function:
var print = function(o){
var str='';
for(var p in o){
if(typeof o[p] == 'string'){
str+= p + ': ' + o[p]+'; </br>';
}else{
str+= p + ': { </br>' + print(o[p]) + '}';
}
}
return str;
}
Usage:
var myObject = {
name: 'Wilson Page',
contact: {
email: 'wilson@hotmail.com',
tel: '123456789'
}
}
$('body').append( print(myObject) );
Example:
In NodeJS you can print an object by using util.inspect(obj)
. Be sure to state the depth or you'll only have a shallow print of the object.
Simply use
JSON.stringify(obj)
Example
var args_string = JSON.stringify(obj);
console.log(args_string);
Or
alert(args_string);
Also, note in javascript functions are considered as objects.
As an extra note :
Actually you can assign new property like this and access it console.log or display it in alert
foo.moo = "stackoverflow";
console.log(foo.moo);
alert(foo.moo);
Here's a way to do it:
console.log("%o", obj);
NB: In these examples, yourObj defines the object you want to examine.
This is the defacto way of showing the contents of an object
console.log(yourObj)
console.log(Object.keys(yourObj));
console.log(Object.values(yourObj));
It will output something like :
(pictured above: the keys/values stored in the object)
Object.keys(yourObj).forEach(e => console.log(`key=${e} value=${yourObj[e]}`));
This will produce neat output :
The solution mentioned in a previous answer:
console.log(yourObj)
displays too many parameters and is not the most user friendly way to display the data you want. That is why I recommend logging keys and then values separately.
console.table(yourObj)
Someone in an earlier comment suggested this one, however it never worked for me. If it does work for someone else on a different browser or something, then kudos! Ill still put the code here for reference!
Will output something like this to the console :
To print the full object with Node.js with colors as a bonus:
console.dir(object, {depth: null, colors: true})
Colors are of course optional, 'depth: null' will print the full object.
The options don't seem to be supported in browsers.
References:
https://developer.mozilla.org/en-US/docs/Web/API/Console/dir
https://nodejs.org/api/console.html#console_console_dir_obj_options
As it was said before best and most simply way i found was
var getPrintObject=function(object)
{
return JSON.stringify(object);
}
(This has been added to my library at GitHub)
Reinventing the wheel here! None of these solutions worked for my situation. So, I quickly doctored up wilsonpage's answer. This one is not for printing to screen (via console, or textfield or whatever). It does work fine in those situations and works just fine as the OP requested, for alert
. Many answers here do not address using alert
as the OP requested. Anyhow, It is, however, formatted for data transport. This version seems to return a very similar result as toSource()
. I've not tested against JSON.stringify
, but I assume this is about the same thing. This version is more like a poly-fil so that you can use it in any environment. The result of this function is a valid Javascript object declaration.
I wouldn't doubt if something like this was already on SO somewhere, but it was just shorter to make it than to spend a while searching past answers. And since this question was my top hit on google when I started searching about this; I figured putting it here might help others.
Anyhow, the result from this function will be a string representation of your object, even if your object has embedded objects and arrays, and even if those objects or arrays have even further embedded objects and arrays. (I heard you like to drink? So, I pimped your car with a cooler. And then, I pimped your cooler with a cooler. So, your cooler can drink, while your being cool.)
Arrays are stored with []
instead of {}
and thus dont have key/value pairs, just values. Like regular arrays. Therefore, they get created like arrays do.
Also, all string (including key names) are quoted, this is not necessary unless those strings have special characters (like a space or a slash). But, I didn't feel like detecting this just to remove some quotes that would otherwise still work fine.
This resulting string can then be used with eval
or just dumping it into a var thru string manipulation. Thus, re-creating your object again, from text.
function ObjToSource(o){
if (!o) return 'null';
var k="",na=typeof(o.length)=="undefined"?1:0,str="";
for(var p in o){
if (na) k = "'"+p+ "':";
if (typeof o[p] == "string") str += k + "'" + o[p]+"',";
else if (typeof o[p] == "object") str += k + ObjToSource(o[p])+",";
else str += k + o[p] + ",";
}
if (na) return "{"+str.slice(0,-1)+"}";
else return "["+str.slice(0,-1)+"]";
}
Let me know if I messed it all up, works fine in my testing. Also, the only way I could think of to detect type array
was to check for the presence of length
. Because Javascript really stores arrays as objects, I cant actually check for type array
(there is no such type!). If anyone else knows a better way, I would love to hear it. Because, if your object also has a property named length
then this function will mistakenly treat it as an array.
EDIT: Added check for null valued objects. Thanks Brock Adams
EDIT: Below is the fixed function to be able to print infinitely recursive objects. This does not print the same as toSource
from FF because toSource
will print the infinite recursion one time, where as, this function will kill it immediately. This function runs slower than the one above, so I'm adding it here instead of editing the above function, as its only needed if you plan to pass objects that link back to themselves, somewhere.
const ObjToSource=(o)=> {
if (!o) return null;
let str="",na=0,k,p;
if (typeof(o) == "object") {
if (!ObjToSource.check) ObjToSource.check = new Array();
for (k=ObjToSource.check.length;na<k;na++) if (ObjToSource.check[na]==o) return '{}';
ObjToSource.check.push(o);
}
k="",na=typeof(o.length)=="undefined"?1:0;
for(p in o){
if (na) k = "'"+p+"':";
if (typeof o[p] == "string") str += k+"'"+o[p]+"',";
else if (typeof o[p] == "object") str += k+ObjToSource(o[p])+",";
else str += k+o[p]+",";
}
if (typeof(o) == "object") ObjToSource.check.pop();
if (na) return "{"+str.slice(0,-1)+"}";
else return "["+str.slice(0,-1)+"]";
}
Test:
var test1 = new Object();
test1.foo = 1;
test1.bar = 2;
var testobject = new Object();
testobject.run = 1;
testobject.fast = null;
testobject.loop = testobject;
testobject.dup = test1;
console.log(ObjToSource(testobject));
console.log(testobject.toSource());
Result:
{'run':1,'fast':null,'loop':{},'dup':{'foo':1,'bar':2}}
({run:1, fast:null, loop:{run:1, fast:null, loop:{}, dup:{foo:1, bar:2}}, dup:{foo:1, bar:2}})
NOTE: Trying to print document.body
is a terrible example. For one, FF just prints an empty object string when using toSource
. And when using the function above, FF crashes on SecurityError: The operation is insecure.
. And Chrome will crash on Uncaught RangeError: Maximum call stack size exceeded
. Clearly, document.body
was not meant to be converted to string. Because its either too large, or against security policy to access certain properties. Unless, I messed something up here, do tell!
If you would like to print the object of its full length, can use
console.log(require('util').inspect(obj, {showHidden: false, depth: null})
If you want to print the object by converting it to the string then
console.log(JSON.stringify(obj));
I needed a way to recursively print the object, which pagewil's answer provided (Thanks!). I updated it a little bit to include a way to print up to a certain level, and to add spacing so that it is properly indented based on the current level that we are in so that it is more readable.
// Recursive print of object
var print = function( o, maxLevel, level ) {
if ( typeof level == "undefined" ) {
level = 0;
}
if ( typeof level == "undefined" ) {
maxLevel = 0;
}
var str = '';
// Remove this if you don't want the pre tag, but make sure to remove
// the close pre tag on the bottom as well
if ( level == 0 ) {
str = '<pre>';
}
var levelStr = '';
for ( var x = 0; x < level; x++ ) {
levelStr += ' ';
}
if ( maxLevel != 0 && level >= maxLevel ) {
str += levelStr + '...</br>';
return str;
}
for ( var p in o ) {
if ( typeof o[p] == 'string' ) {
str += levelStr +
p + ': ' + o[p] + ' </br>';
} else {
str += levelStr +
p + ': { </br>' + print( o[p], maxLevel, level + 1 ) + levelStr + '}</br>';
}
}
// Remove this if you don't want the pre tag, but make sure to remove
// the open pre tag on the top as well
if ( level == 0 ) {
str += '</pre>';
}
return str;
};
Usage:
var pagewilsObject = {
name: 'Wilson Page',
contact: {
email: 'wilson@hotmail.com',
tel: '123456789'
}
}
// Recursive of whole object
$('body').append( print(pagewilsObject) );
// Recursive of myObject up to 1 level, will only show name
// and that there is a contact object
$('body').append( print(pagewilsObject, 1) );
You can also use ES6 template literal concept to display the content of a JavaScript object in a string format.
alert(`${JSON.stringify(obj)}`);
const obj = {
"name" : "John Doe",
"habbits": "Nothing",
};
alert(`${JSON.stringify(obj)}`);
I always use console.log("object will be: ", obj, obj1)
.
this way I don't need to do the workaround with stringify with JSON.
All the properties of the object will be expanded nicely.
Another way of displaying objects within the console is with JSON.stringify
. Checkout the below example:
var gandalf = {
"real name": "Gandalf",
"age (est)": 11000,
"race": "Maia",
"haveRetirementPlan": true,
"aliases": [
"Greyhame",
"Stormcrow",
"Mithrandir",
"Gandalf the Grey",
"Gandalf the White"
]
};
//to console log object, we cannot use console.log("Object gandalf: " + gandalf);
console.log("Object gandalf: ");
//this will show object gandalf ONLY in Google Chrome NOT in IE
console.log(gandalf);
//this will show object gandalf IN ALL BROWSERS!
console.log(JSON.stringify(gandalf));
//this will show object gandalf IN ALL BROWSERS! with beautiful indent
console.log(JSON.stringify(gandalf, null, 4));
Javascript Function
<script type="text/javascript">
function print_r(theObj){
if(theObj.constructor == Array || theObj.constructor == Object){
document.write("<ul>")
for(var p in theObj){
if(theObj[p].constructor == Array || theObj[p].constructor == Object){
document.write("<li>["+p+"] => "+typeof(theObj)+"</li>");
document.write("<ul>")
print_r(theObj[p]);
document.write("</ul>")
} else {
document.write("<li>["+p+"] => "+theObj[p]+"</li>");
}
}
document.write("</ul>")
}
}
</script>
Printing Object
<script type="text/javascript">
print_r(JAVACRIPT_ARRAY_OR_OBJECT);
</script>
var list = function(object) {
for(var key in object) {
console.log(key);
}
}
where object
is your object
or you can use this in chrome dev tools, "console" tab:
console.log(object);
Assume object obj = {0:'John', 1:'Foo', 2:'Bar'}
Print object's content
for (var i in obj){
console.log(obj[i], i);
}
Console output (Chrome DevTools) :
John 0
Foo 1
Bar 2
Hope that helps!
I prefer using console.table
for getting clear object format, so imagine you have this object:
const obj = {name: 'Alireza', family: 'Dezfoolian', gender: 'male', netWorth: "$0"};
And you will you see a neat and readable table like this below:
To make string without redundant information from object which contains duplicate references (references to same object in many places) including circular references, use JSON.stringify
with replacer (presented in snippet) as follows
let s = JSON.stringify(obj, refReplacer(), 4);
function refReplacer() {
let m = new Map(), v= new Map(), init = null;
return function(field, value) {
let p= m.get(this) + (Array.isArray(this) ? `[${field}]` : '.' + field);
let isComplex= value===Object(value)
if (isComplex) m.set(value, p);
let pp = v.get(value)||'';
let path = p.replace(/undefined\.\.?/,'');
let val = pp ? `#REF:${pp[0]=='[' ? '$':'$.'}${pp}` : value;
!init ? (init=value) : (val===init ? val="#REF:$" : 0);
if(!pp && isComplex) v.set(value, path);
return val;
}
}
// ---------------
// TEST
// ---------------
// gen obj with duplicate references
let a = { a1: 1, a2: 2 };
let b = { b1: 3, b2: "4" };
let obj = { o1: { o2: a }, b, a }; // duplicate reference
a.a3 = [1,2,b]; // circular reference
b.b3 = a; // circular reference
let s = JSON.stringify(obj, refReplacer(), 4);
console.log(s);
alert(s);
This solution based on this (more info there) create JSONPath like path for each object value and if same object occurs twice (or more) it uses reference with this path to reference that object e.g. #REF:$.bar.arr[3].foo
(where $
means main object) instead 'render' whole object (which is less redundant)
BONUS: inversion
function parseRefJSON(json) {
let objToPath = new Map();
let pathToObj = new Map();
let o = JSON.parse(json);
let traverse = (parent, field) => {
let obj = parent;
let path = '#REF:$';
if (field !== undefined) {
obj = parent[field];
path = objToPath.get(parent) + (Array.isArray(parent) ? `[${field}]` : `${field?'.'+field:''}`);
}
objToPath.set(obj, path);
pathToObj.set(path, obj);
let ref = pathToObj.get(obj);
if (ref) parent[field] = ref;
for (let f in obj) if (obj === Object(obj)) traverse(obj, f);
}
traverse(o);
return o;
}
// ------------
// TEST
// ------------
let s = `{
"o1": {
"o2": {
"a1": 1,
"a2": 2,
"a3": [
1,
2,
{
"b1": 3,
"b2": "4",
"b3": "#REF:$.o1.o2"
}
]
}
},
"b": "#REF:$.o1.o2.a3[2]",
"a": "#REF:$.o1.o2"
}`;
console.log('Open Chrome console to see nested fields');
let obj = parseRefJSON(s);
console.log(obj);
A little helper function I always use in my projects for simple, speedy debugging via the console. Inspiration taken from Laravel.
/**
* @param variable mixed The var to log to the console
* @param varName string Optional, will appear as a label before the var
*/
function dd(variable, varName) {
var varNameOutput;
varName = varName || '';
varNameOutput = varName ? varName + ':' : '';
console.warn(varNameOutput, variable, ' (' + (typeof variable) + ')');
}
Usage
var obj = {field1: 'xyz', field2: 2016};
dd(obj, 'My Cool Obj');
The console.log() does a great job of debugging objects, but if you are looking to print the object to the page content, here's the simplest way that I've come up with to mimic the functionality of PHP's print_r(). A lot these other answers want to reinvent the wheel, but between JavaScript's JSON.stringify() and HTML's <pre> tag, you get exactly what you are looking for.
var obj = { name: 'The Name', contact: { email: 'thename@gmail.com', tel: '123456789' }};
$('body').append('<pre>'+JSON.stringify(obj, null, 4)+'</pre>');
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
i used pagewil's print method, and it worked very nicely.
here is my slightly extended version with (sloppy) indents and distinct prop/ob delimiters:
var print = function(obj, delp, delo, ind){
delp = delp!=null ? delp : "\t"; // property delimeter
delo = delo!=null ? delo : "\n"; // object delimeter
ind = ind!=null ? ind : " "; // indent; ind+ind geometric addition not great for deep objects
var str='';
for(var prop in obj){
if(typeof obj[prop] == 'string' || typeof obj[prop] == 'number'){
var q = typeof obj[prop] == 'string' ? "" : ""; // make this "'" to quote strings
str += ind + prop + ': ' + q + obj[prop] + q + '; ' + delp;
}else{
str += ind + prop + ': {'+ delp + print(obj[prop],delp,delo,ind+ind) + ind + '}' + delo;
}
}
return str;
};
Another modification of pagewils code... his doesn't print out anything other than strings and leaves the number and boolean fields blank and I fixed the typo on the second typeof just inside the function as created by megaboss.
var print = function( o, maxLevel, level )
{
if ( typeof level == "undefined" )
{
level = 0;
}
if ( typeof maxlevel == "undefined" )
{
maxLevel = 0;
}
var str = '';
// Remove this if you don't want the pre tag, but make sure to remove
// the close pre tag on the bottom as well
if ( level == 0 )
{
str = '<pre>'; // can also be <pre>
}
var levelStr = '<br>';
for ( var x = 0; x < level; x++ )
{
levelStr += ' '; // all those spaces only work with <pre>
}
if ( maxLevel != 0 && level >= maxLevel )
{
str += levelStr + '...<br>';
return str;
}
for ( var p in o )
{
switch(typeof o[p])
{
case 'string':
case 'number': // .tostring() gets automatically applied
case 'boolean': // ditto
str += levelStr + p + ': ' + o[p] + ' <br>';
break;
case 'object': // this is where we become recursive
default:
str += levelStr + p + ': [ <br>' + print( o[p], maxLevel, level + 1 ) + levelStr + ']</br>';
break;
}
}
// Remove this if you don't want the pre tag, but make sure to remove
// the open pre tag on the top as well
if ( level == 0 )
{
str += '</pre>'; // also can be </pre>
}
return str;
};
Here's function.
function printObj(obj) {
console.log((function traverse(tab, obj) {
let str = "";
if(typeof obj !== 'object') {
return obj + ',';
}
if(Array.isArray(obj)) {
return '[' + obj.map(o=>JSON.stringify(o)).join(',') + ']' + ',';
}
str = str + '{\n';
for(var p in obj) {
str = str + tab + ' ' + p + ' : ' + traverse(tab+' ', obj[p]) +'\n';
}
str = str.slice(0,-2) + str.slice(-1);
str = str + tab + '},';
return str;
}('',obj).slice(0,-1)))};
It can show object using tab indent with readability.
If you're looking for something that can return a prettified string of any javascript object, check out https://github.com/fresheneesz/beautinator . An example:
var result = beautinator({ "font-size": "26px","font-family": "'Open Sans', sans-serif",color: "white", overflow: "hidden",padding: "4px 4px 4px 8px",Text: { display: "block", width: "100%","text-align": "center", "padding-left": "2px","word-break": "break-word"}})
console.log(result)
Results in:
{ "font-size": "26px",
"font-family": "'Open Sans', sans-serif",
color: "white", overflow: "hidden",
padding: "4px 4px 4px 8px",
Text: { display: "block", width: "100%",
"text-align": "center", "padding-left": "2px",
"word-break": "break-word"
}
}
It even works if there are functions in your object.
A simple way to show the contents of the object is using console.log as shown below
console.log("Object contents are ", obj);
Please note that I am not using '+' to concatenate the object. If I use '+' than I will only get the string representation if object, something like [Object object].
In ES2015, using the shorthand property declaration syntax for object literals, you can log objects while also concisely preserving your variable names:
console.log("bwib:", bwib, "bwab:", bwab, "bwob": bwob) // old way A
console.log({bwib: bwib, bwab: bwab, bwob: bwob}) // old way B
console.log({bwib, bwab, bwob}) // ES2015+ way
It will not work in a browser and you might only need this in case you want to get valid JS representation for your object and not a JSON. It just runs node inline evaluation
var execSync = require('child_process').execSync
const objectToSource = (obj) =>
execSync('node -e \'console.log(JSON.parse(`' + JSON.stringify(obj) + '`))\'', { encoding: 'utf8' })
console.log(objectToSource({ a: 1 }))
I am astounded this doesn't have a simpler answer, just a bunch of people repeating the exact same 2 things and others with unreadable code...
Here you go. If you just need the object as a string (no nested levels):
function prettyStringifyObject(obj: Record < any, any > ) {
let result = ''
for (const key in obj) {
result = `${result}${result !== '' ? ', ' : ''}${key}: ${Array.isArray(obj[key]) ? `[${obj[key]}]` : obj[key]}`
}
return `{${result}}`
}
Test with
const someTestObject = {
data: [1, 2, 3, "4"],
aString: "awdasdyhblhyb",
aBoolean: true,
aNumber: 50,
aNull: null
aNestedObject: {
someOtherData: [],
isNested: true
}
}
console.log(prettyStringifyObject(someTestObject))
Result:
"{data: [1,2,3,4], aString: awdasdyhblhyb, aBoolean: true, aNumber: 50, aNull: null, aNestedObject: [object Object]}"
You can check the JSFiddle I made here
You may use my function .
Call this function with an array or string or an object it alerts the contents.
Function
function print_r(printthis, returnoutput) {
var output = '';
if($.isArray(printthis) || typeof(printthis) == 'object') {
for(var i in printthis) {
output += i + ' : ' + print_r(printthis[i], true) + '\n';
}
}else {
output += printthis;
}
if(returnoutput && returnoutput == true) {
return output;
}else {
alert(output);
}
}
Usage
var data = [1, 2, 3, 4];
print_r(data);
It seems that a simple for...in
can't solve the problem especially when we want to tackle apart from custom, host , native or CSSOM objects. Besides, we are talking about debugging here and who knows when and where we'll need it!
My small library can handle objects like this one:
obj2
|__ foo = 'bar'
|__ loop2 = obj2
| :
|__ another = obj1
|__ a1 = 1
|__ b1 = 'baz'
|__ loop1 = obj1
| :
|__ c1 = true
|__ d1 = ''
|__ e1 = [1,2,3]
and present them colorful and with identation like:
but see there:
With some precautions even document.body
is parsed!