What are the most Javascript common typing code errors?*

Can anyone please tell me What are the most Javascript common typing code errors.

JavaScript is criticized as a language that is quite difficult to debug. It doesn’t matter how perfect the code of a front-end application is, some of its functionality will get impacted especially when we get down to test it’s compatbility across different browsers. The errors occur mostly because many times developers use modern Web API or ECMA 6 scripts in their codes that are not yet browser compatible even in some most popular browser versions. In this article, we will look at the errors commonly faced by developers in their front-end application and how to minimize or get rid of them.

Uncaught TypeError

If you are debugging your JavaScript code in Google Chrome, you may have seen this error for several times. This occurs when you call a method or read a property on an undefined object.

Although this error can occur due to many reasons, a common one is the state of an element not properly initialized when UI components are rendered. Not only in JavaScript, this issue can also occur in an application developed using React JS or Angular jS. Let’s see how to fix it.

Fix – The state should be initialized using a reasonable default value in constructors.

TypeError – Property Not Supported by Object

This error usually occurs in Internet Explorer when an undefined method is called. It can be compared to the undefined function error that occur in Chrome. For web applications that use JavaScript namespacing, this error is quite common. IE cannot bind “this” keyword to the current namespace. For example, this.isAwesome() works properly in all browsers but throws an exception in Chrome.

Fix – When using namespacing, this error can be avoided by using the actual namespace as a prefix

TypeError – Cannot Read Length

This error occurs mostly in Chrome due to an undefined variable’s length property. Normally an array has its length defined. But when the variable name of an array remains hidden or if the array is not initialized, this error happens.

Fix – This error can be fixed in 2 ways

In the statement where the function is declared, parameters should be removed. The function should be invoked in the array that is declared. Most of the errors that occur when the browser compiles the JavaScript are either undefined or null type errors. If the developer uses the strict compiler in a static checking system like Typescript, these errors can be avoided. It will give the warning that a type is not defined but expected. Even if Typescript is not used, guard clauses can be used to check if the objects are undefined before they are used.