core-localstorage defaulting logic has bad null test

[sjmiles]

If there no value is in localstorage, core-localstorage tries not to create one unless it looks like the user has set a real value. However, the conditional is written such that a value of undefined does get saved.

https://github.com/Polymer/core-localstorage/blob/master/core-localstorage.html#L100

Should probably be:

if (this.value !== null && this.value !== undefined) {

[jmesserly]

fwiw, I think

if (this.value != null) {

is equivalent to

if (this.value !== null && this.value !== undefined) {

... I tend to use the former as it's a bit more concise.

[jmesserly]

(wanted to double check this, so found the relevant spec for == https://people.mozilla.org/~jorendorff/es6-draft.html#sec-abstract-equality-comparison)

[sjmiles]

You are right about that, and it's definitely more concise. OTOH, it's one of the most confusing bits of Javascript: null == undefined but null != false but Boolean(null) == false (so if (null) is false).

This is the main reason we prefer ===, and I'm inclined to be explicit in these cases. But it could go either way.

[sjmiles]

Depending on my mood, I'm waffling between brevity and clarity.

We could make a Polymer.defined method to try to split the difference (defined(value) is true if value != null). Eh, it's not worth the trouble.

[tomalec]

Thanks guys! You're fixing bugs faster than I'm able to isolate them from my app ;)