What is the best way to check if a variable in my JavaScript code has been assigned a value?
This assessment should yield a negative result for
var bar;
and a positive result for
var bar = "hello";
What is the best way to check if a variable in my JavaScript code has been assigned a value?
This assessment should yield a negative result for
var bar;
and a positive result for
var bar = "hello";
if (bar === undefined) { /* not initialized */ }
or for the overly cautious
if (bar === (void) 0)
Testing this kind of scenario can be easily done in your JavaScript console. Simply create a variable and then try using it in an expression. The output in the console will give you a clue on how to proceed.
When utilizing the typeof operator, you can conduct the following test:
if (typeof foo !== 'undefined') {
// foo is defined and set to 5
}
else {
// foo is not defined
}
The jQuery fundamentals JavaScript Basics chapter is a valuable resource in my opinion.
I trust that this explanation will be beneficial to you.
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