CODEWITHSUNDEEP
javascriptexceptionweb-applicationssentry
Piotr Sobczyk
Piotr Sobczyk

Reputation: 6583

"null is not an object" in n.parentNode.removeChild expression

Problem: I'm getting following error reports from the webpage on production: 

TypeErrores6-shim/es6-shim in process
null is not an object (evaluating 'n.parentNode.removeChild')

Question

On the low level, what is the most likely scenario?

  1. n is null (whatever n is)
  2. n.parentNode is null
  3. arg is null in n.parentNode.removeChild(arg)

More details (if relevant):

We're using Sentry error reporting system to report errors.

This error happens under Mobile Safari and Chrome Mobile.

The source maps seems to be broken so I don't know which line of es6-shim script the error refers to (and most likely it's es6-shim problem at all as there is no occurence of removeChild in es6-shim code).

Upvotes: 0

Views: 1748

Answers (1)

T.J. Crowder
T.J. Crowder

Reputation: 1074335

You can easily set up all three situations to determine which it is (also on jsFiddle):

var n, p;

console.log("If n were null:")
try {
  n = null;
  n.parentNode.removeChild(null);
} catch (e1) {
  console.log(e1.message);
}

console.log("If parentNode were null:")
try {
  n = document.createElement("div");
  n.parentNode.removeChild(null);
} catch (e2) {
  console.log(e2.message);
}

console.log("If arg were null:")
try {
  p = document.createElement("div");
  n = document.createElement("div");
  p.appendChild(n);
  n.parentNode.removeChild(null);
} catch (e3) {
  console.log(e3.message);
}
.as-console-wrapper {
  max-height: 100% !important;
}

When I run that on mobile Chrome, I see:

If n were null:
null is not an object (evaluating 'n.parentNode')
If parentNode were null:
null is not an object (evaluating 'n.parentNode.removeChild')
If arg were null:
Argument 1 ('child') to Node.removeChild must be an instance of Node

So it would appear that n.parentNode.removeChild(...) is being called on an object referenced by n where parentNode is null.

Although the error is reported in es6-shim, it's not likely to be an error in es6-shim itself (as you say, there's no removeNode in es6-shim); it's more likely that it's being thrown from a callback provided to one of the es6-shim functions.

Upvotes: 2

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