Type error: Object is possibly 'null'. TS2531 for window.document

Question

Adding Typescript to my project for the first time.

At one place i have used window.document.getElementById to access something. And its giving this error.

Type error: Object is possibly 'null'.  TS2531 

I searched online but couldn't come to the best solution for this. window can't ever be null. How can i fix this error? Pls help.

Answer 1

TS is doing its job and tells you that window.document.getElementById("foobar") COULD return something that is null.

If you are absolutely sure that #foobar element DOES exist in your DOM, you can show TS your confidence with a ! operator.

// Notice the "!" at the end of line const myAbsolutelyNotNullElement = window.document.getElementById("foobar")! 

Or, you can add a runtime nullable check to make TS happy

const myMaybeNullElement = window.document.getElementById("foobar")  myMaybeNullElement.nodeName // <- error!  if (myMaybeNullElement === null) {   alert('oops'); } else {   // since you've done the nullable check   // TS won't complain from this point on   myMaybeNullElement.nodeName // <- no error }