Uncaught Typeerror: cannot read property 'innerHTML' of null

Question

Can anyone explain what is theses errors?

Uncaught TypeError: cannot read property \'innerHTML\' of null

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Answer 1

If the script is in the head of your HTML document, the body of your HTML document has not yet been created by the browser, regardless of what will eventually be there (the same result occurs if your script is in the HTML file but above the element). When your variable tries to find document.getElementById("status") it does not yet exist, and so it returns a value of null. When you then use the variable later in your code, the initial value (null) is used and not the current one, because nothing has updated the variable.

I didn't want to move my script link out of the HTML head, so instead I did this in my JS file:

var idPost //define a global variable
function updateVariables(){
    idPost = document.getElementById("status").innerHTML; //update the global variable
}

And this in the HTML file:

If you already have an onload function in place, you can just add the additional line to it or call the function.

If you don't want the variable to be global, define it locally in the function that you are trying to run and make sure the function is not called before the page has fully loaded.