Answers for "javascript how to check if variable is undefined"

19

javascript check if not undefined

if (typeof myVar !== "undefined") {
    console.log("myVar is DEFINED");
}
Posted by: Guest on October-23-2019
7

javascript if undefined

if(typeof comment === 'undefined') {

  alert('Variable "comment" is undefined.');

} else if(comment === null){

  alert('Variable "comment" is null.');

}
Posted by: Guest on March-25-2020
2

test if is undefined javascript

let id;

if(typeof id === 'undefined') {
    console.log("id is undefined...");
}
Posted by: Guest on August-10-2020
1

javascript check if boolean is undefined

if (typeof myFlag !== "undefined") {
  // comes here whether myFlag is true or false but not defined
}
Posted by: Guest on May-02-2020
0

nodejs check if variable is undefined

if ( typeof query !== 'undefined' && query )
{
  //do stuff if query is defined and not null
}
else
{

}
Posted by: Guest on December-25-2020
-1

undefined javascript check

if(undefinedElement === null) {
	console.log("Element is undefined");
}
Posted by: Guest on March-30-2020

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