[javascript] ReferenceError: variable is not defined

Variables are available only in the scope you defined them. If you define a variable inside a function, you won't be able to access it outside of it.

Define variable with var outside the function (and of course before it) and then assign 10 to it inside function:

var value;
$(function() {
  value = "10";
});
console.log(value); // 10

Note that you shouldn't omit the first line in this code (var value;), because otherwise you are assigning value to undefined variable. This is bad coding practice and will not work in strict mode. Defining a variable (var variable;) and assigning value to a variable (variable = value;) are two different things. You can't assign value to variable that you haven't defined.

It might be irrelevant here, but $(function() {}) is a shortcut for $(document).ready(function() {}), which executes a function as soon as document is loaded. If you want to execute something immediately, you don't need it, otherwise beware that if you run it before DOM has loaded, value will be undefined until it has loaded, so console.log(value); placed right after $(function() {}) will return undefined. In other words, it would execute in following order:

var value;
console.log(value);
value = "10";

See also:

Examples related to javascript

need to add a class to an element How to make a variable accessible outside a function? Hide Signs that Meteor.js was Used How to create a showdown.js markdown extension Please help me convert this script to a simple image slider Highlight Anchor Links when user manually scrolls? Summing radio input values How to execute an action before close metro app WinJS javascript, for loop defines a dynamic variable name Getting all files in directory with ajax

Examples related to variables

When to create variables (memory management) How to print a Groovy variable in Jenkins? What does ${} (dollar sign and curly braces) mean in a string in Javascript? How to access global variables How to initialize a variable of date type in java? How to define a variable in a Dockerfile? Why does foo = filter(...) return a <filter object>, not a list? How can I pass variable to ansible playbook in the command line? How do I use this JavaScript variable in HTML? Static vs class functions/variables in Swift classes?

Examples related to definition

"Multiple definition", "first defined here" errors SOAP vs REST (differences) Error with multiple definitions of function ReferenceError: variable is not defined C# Foreach statement does not contain public definition for GetEnumerator Add Auto-Increment ID to existing table? How to see the CREATE VIEW code for a view in PostgreSQL? Java: int[] array vs int array[] What is a web service endpoint? What is a "thread" (really)?

Examples related to var

how to display a javascript var in html body ReferenceError: variable is not defined Initialize value of 'var' in C# to null What is /var/www/html? How can I write these variables into one line of code in C#? Why should I use var instead of a type? What is the equivalent of the C# 'var' keyword in Java? PHPDoc type hinting for array of objects? What's the difference between using "let" and "var"? What is the scope of variables in JavaScript?