I was using console.log() in some JavaScript I wrote and an error of: console is not defined was thrown in Internet Explorer (worked fine in other browsers).
I have replaced it with:
if (console) console.log("...");
If console is undefined, I would expect the condition to evaluate as false. Ergo, the statement console.log wouldn’t be executed and shouldn’t throw an error.
Instead, an error of: console is not defined at character 4 is thrown.
Is this a IE bug? Or is that «if» condition really illegal? It seems absurd because if if (console) is illegal, then if (console==undefined) should be illegal too.
How are you supposed to check for undefined variables?
asked Mar 15, 2012 at 17:36
5
Other answers gave you the root cause.
However, there’s a better solution than using if before any call to console.*
Add this (once) before including any of your scripts that use console:
//Ensures there will be no 'console is undefined' errors
window.console = window.console || (function(){
var c = {}; c.log = c.warn = c.debug = c.info = c.error = c.time = c.dir = c.profile = c.clear = c.exception = c.trace = c.assert = function(s){};
return c;
})();
This will create a ‘pseudo’ console only if it doesn’t exist, so that ‘console is undefined’ errors will go away and you won’t have to ask if console exists everytime.
With this, you just call console.log or any console method anywhere, without problems.
Hope this helps.
Cheers
answered Jul 24, 2012 at 20:14
2
If console itself doesn’t exist at all, it throws an error because you’re accessing an undefined variable. Just like if(abc) {} throws an error.
Since console resides in window, and window does always exist, this should work:
if(window.console) ...
Basically, accessing an property that doesn’t exist is free and doesn’t throw an error (it just evaluates to undefined, failing the if condition). However, it is illegal to access an undeclared variable.
answered Mar 15, 2012 at 17:38
pimvdbpimvdb
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5
in internet explorer the console object is not actually defined unless your developer tools are open at the time the window loads.
to fix your problem, wrap all your console prints in an if statement:
if (typeof window.console !== 'undefined') {
...
}
you also need to refresh each page after you open the developer tools in order to see the console prints. <3 IE
answered Mar 15, 2012 at 17:40
jbabeyjbabey
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1
This is a funny thing about undeclared variables. The JS engine tries to resolve the variable to a property of window. So usually, foo == window.foo.
But, if that property does not exist, it throws an error.
alert(foo); // Syntax error: foo is not defined
(Should be «foo is not declared» imho, but whatever.) That error does not occur when you explicitly reference the window’s property:
alert(window.foo); // undefined
…or declare that variable:
var foo;
alert(foo); // undefined
…or use it for initialization:
foo = 1; // window.foo = 1
The strange thing is that the typeof operator also prevents this error:
alert(typeof foo); // "undefined"
So, to sum things up: You cannot use undeclared variables in expressions unless there’s a property of window with the same name, or you use it as an operand of typeof. In your example, window.console does not exist, and there’s no var declaration. That’s why you get an error.
answered Mar 16, 2012 at 0:57
user123444555621user123444555621
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How about this? Haven’t tried it though
if (typeof console == "undefined" || typeof console.log == "undefined") var console = { log: function() {} };
answered Mar 15, 2012 at 17:40
Chetter HumminChetter Hummin
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0
Edit of @yckart’s answer
Using c.length as input to a function which defines c won’t work. Also you’re just reassigning items in the array with noop when you should be adding methods to window.console.
(function(w){
var c = 'assert,clear,count,debug,dir,dirxml,error,exception,group,groupCollapsed,groupEnd,info,log,markTimeline,profile,profileEnd,table,time,timeEnd,timeStamp,trace,warn'.split(','),
noop = function () {};
w.console = w.console || (function (len) {
var ret = {};
while (len--) { ret[c[len]] = noop; }
return ret;
}(c.length));
})(window);
answered Oct 30, 2013 at 12:56
You can use the below to give an extra degree of insurance that you’ve got all bases covered. Using typeof first will avoid any undefined errors. Using === will also ensure that the name of the type is actually the string «undefined». Finally, you’ll want to add a parameter to the function signature (I chose logMsg arbitrarily) to ensure consistency, since you do pass whatever you want printed to the console to the log function. This also keep you intellisense accurate and avoids any warnings/errors in your JS aware IDE.
if(!window.console || typeof console === "undefined") {
var console = { log: function (logMsg) { } };
}
answered Feb 4, 2013 at 23:56
Flak DiNennoFlak DiNenno
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Inspired by @Edgar Villegas Alvarado answer, completed the methods and made it a bit simpler:
(function(w){
var c = 'assert,clear,count,debug,dir,dirxml,error,exception,group,groupCollapsed,groupEnd,info,log,markTimeline,profile,profileEnd,table,time,timeEnd,timeStamp,trace,warn'.split(','),
noop = function () {};
w.console = w.console || (function (len) {
var ret = {};
while (len--) { ret[c[len]] = noop; }
return ret;
}(c.length));
})(window);
Edited to put into an IIFE and fix a syntax error!
answered Feb 14, 2013 at 8:35
yckartyckart
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Some browsers do not have console enabled when the dev-tools is closed. Also, one would encounter this issue with WebViews or iFrames where console is disabled.
The error in these cases is — Uncaught ReferenceError: console is not defined
Inspired by many answers on here, I developed a library for this usecase: https://github.com/sunnykgupta/jsLogger
Features:
- It safely overrides the console.log.
- Takes care if the console is not available (oh yes, you need to factor that too.)
- Stores all logs (even if they are suppressed) for later retrieval.
- Handles major console functions like
log,warn,error,info.
answered May 21, 2018 at 9:14
Sunny R GuptaSunny R Gupta
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The ‘console is not defined’ error in JavaScript occurs when you try to access the console object, which is typically used for logging information in the browser’s developer tools, from a script running in an environment that doesn’t have access to the console. This error is commonly encountered in text editors like Brackets and can be caused by a number of different factors, including attempting to run JavaScript code outside of a browser environment, misconfigured or missing developer tools, or simply forgetting to include the necessary code to initialize the console object.
Method 1: Run Code in a Browser Environment
To fix the error «console is not defined» in a browser environment, you need to ensure that your code is running in a browser context. One way to do this is to use the «Run Code in a Browser Environment» feature in Brackets.
Here are the steps to fix the error:
- Open your JavaScript file in Brackets.
- Click on the «Live Preview» button in the top right corner of the editor.
- In the Live Preview window, click on the «Run Code in a Browser Environment» button.
- This will open a new browser window with your code running in a browser context.
- In your code, use the console object to log messages to the browser console.
Here is an example code snippet:
console.log("Hello, world!");This will log the message «Hello, world!» to the browser console.
You can also use other console methods, such as console.error, console.warn, and console.info, to log different types of messages to the console.
console.error("An error occurred!");
console.warn("Warning: This action cannot be undone!");
console.info("Information: Your session has expired.");By running your code in a browser context, you can use the console object to debug your code and log messages to the console. This will help you identify and fix errors in your code.
To fix the error «console is not defined» in Brackets, you can check your Developer Tools Configuration. Here are the steps:
- Open your Brackets editor and click on «Debug» in the top menu bar.
- Click on «Open Preferences File».
- Scroll down to the «language-javascript» section.
- Add the following line of code:
- Save the changes to the preferences file.
This will enable the console object to be recognized by the Brackets editor, and the error should disappear.
Here is the code example:
console.log("Hello, world!");This code will output «Hello, world!» to the console.
Another example:
function addNumbers(a, b) {
console.log(a + b);
}
addNumbers(5, 10);This code will output «15» to the console.
In summary, checking your Developer Tools Configuration in Brackets and enabling the «linting.console» option can fix the «console is not defined» error.
Method 3: Include Necessary Code to Initialize Console Object
To fix the error ‘console is not defined’ in JavaScript when using Brackets, you can include the necessary code to initialize the Console object. Here’s how:
- Open your HTML file in Brackets.
- Add the following code to the head section of your HTML file:
<script>
if (!window.console) console = {log: function() {}};
</script>- Save your HTML file and reload it in your browser.
- Open the console in your browser’s developer tools to see the output of your console.log statements.
This code initializes the Console object if it does not already exist. The Console object provides methods for logging information to the browser’s console, such as console.log(). By including this code in your HTML file, you can use console.log() statements in your JavaScript code without encountering the ‘console is not defined’ error.
Here’s an example of how to use console.log() with the initialized Console object:
console.log('Hello, world!');This will log the message ‘Hello, world!’ to the browser’s console.
You can also use other methods provided by the Console object, such as console.error() and console.warn(). Here’s an example of how to use console.error():
console.error('An error occurred!');This will log the message ‘An error occurred!’ to the browser’s console with an error icon.
Overall, including the necessary code to initialize the Console object is a simple and effective way to fix the ‘console is not defined’ error in JavaScript when using Brackets.
Привет. Если есть люди, которые работают с node.js на windows 10 прошу помочь.
Я не давно начал его изучать. Не помню как его устанавливал, я еще разные версии ставил, возможно криво что-то сделал.
Ввожу например в консоль запрос версии и получаю:
$ node -v
bash: node: command not foundв переменных средах системы путь прописан к C:\Program Files\nodejs Но он там то есть, то нет. Сейчас посмотрел нет его, а чуть раньше был и так постоянно. Но, когда он появляется, то папка nodejs выглядит со стрелочкой, как ярлык и в свойствах этого ярлыка путь на AppData/Roaming/непомню/nvm/nodejs
А еще на диске C есть C:\Program Files\nodejsx — то есть с x на конце, вот ее содержимое:
Может это и есть мой nodejs и к нему нужно прописать путь в переменных? или что это вообще такое?
Я вот создал папку, инициализировал в ней npm и создал файл index.js с простым кодом:
console.log("hello");
запускаю node index.js и получаю: «ReferenceError: Console is not defined»
Это может быть как-то связанно? Может стоит все снести и поставить по новой node.js ?
Hi folks,
I am getting a 'console is not defined. (no-undef)` error. I do have both browser and node defined in my eslint config.
However, when I add /*eslint-env browser*/ to a file with a console statement, I don’t get the error. It seems the environment definitions in my eslint.options object are being ignored.
Below is my configuration:
"eslint.options": {
"parserOptions": {
"ecmaVersion": 6
},
"env": {
"es6": true,
"node": true,
"browser": true
},
"rules": {
"arrow-body-style": [2, "always"], // es6
"arrow-parens": [2, "always"], // es6
"arrow-spacing": [1, {"before": true, "after": true}], // es6
"block-scoped-var": 2,
"brace-style": [1, "1tbs", { "allowSingleLine": true }],
"comma-spacing": [1, {"before": false, "after": true}],
"consistent-return": 1,
"constructor-super": 2, // es6
"curly": [2, "all"],
"default-case": 1,
"dot-notation": [1, {"allowKeywords": true}],
"eol-last": 1,
"eqeqeq": 1,
"indent": [1, 4],
"key-spacing": [1, {"beforeColon": false, "afterColon": true}],
"keyword-spacing": [1, {"before": true, "after": true}],
"linebreak-style": [1, "unix"],
"new-cap": [2, {"newIsCap": true, "capIsNew": true, "newIsCapExceptions": [], "capIsNewExceptions": []}],
"new-parens": 2,
"no-case-declarations": 2,
"no-class-assign": 2, // es6
"no-confusing-arrow": [2, {"allowParens": true}], //es6
"no-console": 1,
"no-const-assign": 2, // es6
"no-constant-condition": 2,
"no-div-regex": 2,
"no-dupe-class-members": 2, // es6
"no-else-return": 2,
"no-empty-pattern": 2,
"no-extend-native": 2,
"no-extra-bind": 2,
"no-extra-parens": [1, "all"],
"no-fallthrough": 1,
"no-iterator": 2,
"no-lone-blocks": 2,
"no-loop-func": 1,
"no-multi-spaces": 1, // flags variable `=` alignment
"no-multi-str": 1,
"no-native-reassign": 2,
"no-new-func": 2,
"no-new-wrappers": 2,
"no-octal-escape": 2,
// "no-param-reassign": 2, // flags `myNum += 1`
"no-proto": 2,
"no-return-assign": 2,
"no-script-url": 2,
"no-self-assign": 1,
"no-self-compare": 1,
"no-sequences": 2,
"no-shadow": [2, {"builtinGlobals": true, "hoist": "all", "allow": ["$", "Plugin", "self"]}],
"no-shadow-restricted-names": 2,
"no-spaced-func": 2,
"no-this-before-super": 1, // es6
"no-throw-literal": 2,
"no-trailing-spaces": 1,
"no-undef": 2,
"no-undef-init": 2,
"no-undefined": 2,
"no-unneeded-ternary": 1,
"no-unexpected-multiline": 2,
"no-unused-expressions": [2, {"allowShortCircuit": false, "allowTernary": true}],
"no-unused-vars": [2, {"vars": "all", "args": "after-used"}],
"no-use-before-define": [2, "nofunc"], // exception for function declarations
"no-useless-call": 1,
"no-useless-concat": 1,
"no-void": 2,
"no-with": 2,
"object-curly-spacing": [1, "never"],
"object-shorthand": [1, "never"], // es6
"prefer-arrow-callback": 1, // es6
"prefer-spread": 1, // es6
"quotes": [1, "single"],
"radix": [2, "as-needed"],
"semi": [2, "always"],
"semi-spacing": [1, {"before": false, "after": true}],
"space-before-blocks": [1, {"functions": "always", "keywords": "always"}],
"space-before-function-paren": [1, {"anonymous": "never", "named": "never"}],
"space-in-parens": [1, "never"],
// "space-infix-ops": 1, // flags `'str'+'ing'`
"space-unary-ops": [1, { "words": true, "nonwords": false }],
"spaced-comment": [1, "always", {"exceptions": ["!"]}], // exception for `!`
"vars-on-top": 1,
"wrap-iife": [1, "outside"],
"wrap-regex": 1,
"yoda": [1, "never"]
},
// http://eslint.org/docs/user-guide/configuring#extending-configuration-files
// ---------------------------------------------------------------------------
"extends": "eslint:recommended"
}
In a test.js file, this throws the no-undef error:
const foo = 'bar';
(function() {
console.log(foo);
}());
This does not:
/* eslint-env browser */
const foo = 'bar';
(function() {
console.log(foo);
}());
in internet explorer the console object is not actually defined unless your developer tools are open at the time the window loads. to fix your problem, wrap all your console prints in an if statement: if (typeof window. console !==
What is reference error in node?
Moving along through our detailed Node. If you’re familiar with plain JavaScript ReferenceErrors , the ReferenceError class in Node will look quite familiar, since it performs the same role: When a reference is made to an object that hasn’t been defined in previously executed statements, a ReferenceError is thrown.
How do I stream data in node JS?
In the snippet above the first step is we import the file system package which is an inbuilt package in Node. js. We then initialize an empty string variable data . The statement that follows creates a read stream through the createReadStream method.
What is a reference error in JS?
The ReferenceError object represents an error when a variable that doesn’t exist (or hasn’t yet been initialized) in the current scope is referenced.
How do you check if a variable is not defined in JavaScript?
In JavaScript, a variable can be either defined or not defined, as well as initialized or uninitialized. typeof myVar === ‘undefined’ evaluates to true if myVar is not defined, but also defined and uninitialized. That’s a quick way to determine if a variable is defined.
Is not defined reference error?
This JavaScript exception variable is not defined occurs if there is a non-existent variable that is referenced somewhere. Cause of Error: That variable has to be declared, or make sure the variable is available in the current script or scope. …
Is not defined in JS error?
If you are using jQuery, Angular JS, or plain old JavaScript and getting “Uncaught ReferenceError: $ is not defined” error which means $ is either a variable or a method that you are trying to use before declaring it using the var keyword.
Which object is a stream node JS?
js.” The stream module provides an API for implementing the stream interface. Examples of the stream object in Node. js can be a request to an HTTP server and process. stdout are both stream instances.
What is stream pipe Nodejs?
The readable. pipe() method in a Readable Stream is used to attach a Writable stream to the readable stream so that it consequently switches into flowing mode and then pushes all the data that it has to the attached Writable. Syntax: readable.pipe( destination, options )
Is not defined error in JavaScript?
not defined: In JavaScript, it is one of the reference errors that JavaScript will throw when someone accesses the variable which is not inside the memory heap.
What is the difference between Node JS and chrome JS?
Both Node JS and chrome has Javascript’s V8 engine but both of them are completely different in terms of running js. Your browser is capable of running only client-side javascript. To run this code without any kind of error, you need to install node on your system. Here is a detailed guide on installing node js on Mac, Windows or Linux.
Is windows trying to run JScript on Node JS?
I just installed Node.js on a new system and wanted to make sure it worked. I tested it with a simple hello world script. Weird. And Microsoft JScript runtime? Very weird. Turns out, Windows is trying to run the Javascript, node.js, not via Node.js but natively in Windows.
What is the use of the require function in Node JS?
The require function is the builtin function of node js that helps us to include local or node_modules in our project that exists in a separate file. const express = require (‘express’) const app = express () const port = 3000 app.get (‘/’, (req, res) => res.send (‘Hello World!’)) app.listen (port, () => console.log (‘App is running!’))
How to check which version of node icon I am running?
Even I faced the same when I install the NODE server and Try to execute “node-v” command from directly clicking on start up menu’s NODE ICON. Instead of doing that all you need to do is GO TO command prompt then go to C:/program files/node path and type “node -v” command it will definitely going to display you the version of NODE.
https://www.youtube.com/watch?v=lABwiMj2giY