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Raoul Debergh
Birgitte Hundhammer
Kai Dietrich
Stijn van Driessen

5 Errors in JavaScript Programming

5 min. read time

When we are talking about JavaScript programming, there is a need to understand the areas of programming and also take a very infinite turn in the overall perspective. JavaScript is one of the programming languages that is mostly a part of the biggest development projects.

Today, programming for web applications without JavaScript seems impossible! It is a client side scripting language. Also, there are so many efficient frameworks for JavaScript development like AngularJS, Ext JS, Backbone JS etc. which are being used to build web application for large and medium large companies.

JavaScript Development Agency

The JavaScript Programming

1. ( + ) Symbol is Important

Don’t forget to use the (+) sign while you perform addition or subtraction function while writing the code in JavaScript development. Other scripting language does not use the plus symbol for string concatenation and addition. But this is mainly an important function in JavaScript language and a developer’s needs to be very careful in order to use this function.

Let us take an example:

 The result of the code written above will be x variable equal to 10. As we know in JavaScript, we use mix of strings and numbers due to user input.

 This code will evaluate to “28” as the string and the plus symbol translates to a concatenation symbol. The submission values as input and the user input can be evaluated as a string.

So try using this code instead of the above one. Here, you convert the string value to an integer first.

 When you do this in the code, the string value is parse to the integer value and the addition function is performed.

2. The Use of “IF” Statement Incorrectly

Among the JavaScript developers, this is one of the commonly made mistakes but it has a bigger impact on the code by becoming a major logic bug in the code.

“==” is for the comparison and the “=” is for assigning a value to the variable. This way the error is created depending on the language. In JavaScript, this error is evaluated as the statement and return true or false. 

Let’s take an example:

 According to this entry, the evaluation will be x is equal to 2. And the result stands 2. But what in case the web developer makes a typo error? You can take the following code:

 Using “If” statement is incorrect here and in many cases, JavaScript will showcase this as an error. And in some languages, the error is not in JavaScript. But it can also happen that the result turns out to be true. So a web developer or a JavaScript developer needs to be very careful while using “if” statement.

See Also : Expert Tips For Angular Development

3. Undefined and Null Functions

JavaScript uses undefined and null where you can set null to variable, it defaults variable to undefined and objects to null. For an object to be null, it must be defined, so a developer must be careful when you compare objects.

The following code will give you an error if the object is undefined:

 The object is undefined first, then identify if it’s null.

 4. Named Objects Indexes as Arrays

The arrays use numeric integer indexes where web developers can also use objects similar to arrays but objects uses named indexes. If you attempt using a named index in an array then your code will return the wrong result.

The Following Array:

Here, the color with the name is created by assigning colors to the first three indexes. Further, the evaluation of the length and assigning of the first color to the variable y is done. The evaluation of variable x is 3 and the variable y contains “pink”. Array uses numeric integers and thus when you take an object, the result may be wrong.

5. No Scope for Block Level

In other scripting languages, you can easily create a loop structure through a variable. The loop is created through the variable and it is destroyed once the loop exists.

The output in JavaScript will be slightly different if you have values with 0 in it. It may read as the language quirk.


 JavaScript is a language which is used by web development experts and software development specialist in order to build robust and rich front end applications and web applications. So in cases if you encounter a bug while the development process, you can find the solutions very easily. It is backed by a big community of developers. 

And if you have any query in regard with coding or you need a JavaScript based web application, you can always reach out to us and we will be help you out. We are a team of highly experienced software developers who are experts in various JavaScript frameworks.

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