iron-ajax should handle undefined headers

[kevinpschaaf]

From @mvolkmann on September 28, 2016 15:20

Description

I get the following error if a header has the value undefined:

iron-ajax.html:403 Uncaught TypeError: Cannot read property 'toString' of undefined

This is in the "get requestHeaders" method. Here is the relevant code:

      if (this.headers instanceof Object) {
        for (header in this.headers) {
          headers[header] = this.headers[header].toString();
        }
      }

You might think no header should ever have the value undefined. However, this can happen when setting a header to the value of some other object property. For example,

header[name] = sessionStorage.something;

Here is the fix I suggest:

      if (this.headers instanceof Object) {
        for (header in this.headers) {
          const value = this.headers[header];
          if (value !== undefined) headers[header] = value.toString();
        }
      }

Steps to Reproduce

Set any iron-ajax header to undefined.

Expected Results

Handle this case.

Actual Results

iron-ajax.html:403 Uncaught TypeError: Cannot read property 'toString' of undefined

Browsers Affected

all

Versions

probably all

Copied from original issue: Polymer/polymer#4012