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How do I check for an empty/undefined/null string in JavaScript?


Checking an Empty String in Javascript

JavaScript provides several ways to check if a string is empty. Below are the methods available for checking:

Method 1: Using double equal operator (==)

This is the simplest way to check if a string is empty or not. To check for an empty string in Javascript using this method, you can use the code below:

var myString="";
if(myString == "")

If the string is empty, it will return true.

Method 2: Total string length

Using the length property, we can check that the string is not empty.

var myString="";
if(myString.length == 0)

If the string is empty, it will return true.

Method 3: Using triple equal operator (===)

This method checks for both type and value of the string.

var myString="";
if(myString === "")

If the string is empty, it will return true.

Method 4: Using a function

You can also use a function to check if a string is empty or not.

function isEmpty(str){
return (!str || 0 === str.length);
}

var myString="";
if(isEmpty(myString))

If the string is empty, it will return true.

Method 5: Using Undefined, null or Empty strings

It can be used to check if the string is undefined, null, or an empty string:

var myString="";
if(!myString && myString != "")

If the string is empty, it will return true.

Conclusion

In summary, there are multiple ways to check if a string is empty or not in Javascript, including using the double equal operator (==), the total string length, the triple equal operator (===), a function and using undefined, null or empty strings. Depending on the situation, you can use any of these methods to check if a string is empty.

sa3dy

Mostafa Saady, Egyptian Software Engineer, supersonic self-learner and teacher, fond of learning and exploring new technologies and science. As a self-taught professional I really know the hard parts and the difficult topics when learning new or improving on already-known languages. This background and experience enables me to focus on the most relevant key concepts and topics.

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