Catch reserved keyword

[bashilbers]

This is my script:

importFeed().then(function() {
    self.log.info('Importing feed done');
 }).catch(function(e) { });

My developer console says this: Uncaught TypeError: undefined is not a function

catch is on the reserved list: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Reserved_Words

cite: "...may not be used as ... method"

So, how do I keep track of async errors when I cant call catch on my promise?

[briancavalier]

@bashilbers catch is part of the ES6 Promise standard, so it is allowed as a method in ES5+ environments. For ES3 environments, you can use the alias otherwise.

However, "undefined is not a function" sounds like an unrelated error. Are you sure you're calling catch on a when.js promise, and not some other promise or promise-like, such as a jQuery deferred?

[unscriptable]

Hey @bashilbers,

There are two ways you can use catch in older browsers: a) quote it, b) use an alias.

Quote it

importFeed().then(function() {
    self.log.info('Importing feed done');
 })['catch'](function(e) { });

Alias

otherwise() is an alias for catch(). See the docs: https://github.com/cujojs/when/blob/master/docs/api.md#promisecatch

[briancavalier]

That Mozilla page is a bit confusing. The first sentence seems to be outdated or ES3-specific. Have a look at the ES5 section of that Mozilla link for info on ES5 (and later) envs.

[bashilbers]

I'm using otherwise now, which is working for me

[briancavalier]

Cool, glad that worked for you. There are aliases for the other ES3 reserved words as well, eg finally -> ensure.