How object properties accessed in the given JS code?

Question

I have seen the following two codes on the internet and I can't really understand how they are being parsed and executed. BTW I am new to ES6.

return getUsername()
.then(function (username) {
    return getUser(username);
})
.then(function (user) {
});

Is it correct to interpret the above code as:

return getUsername().then(function(username){return getUser(username);}).then(function (user){});

Or Does it have some different meaning in the ES6?

Similarly in the following:

new Q(value)
.then(function(/*Success handler*/){}, function(/*Failure handler*/){})

Should it be interpreted as:

new Q(value).then(function(/*Success handler*/){},function(/*Failure handler*/){})

In general, white spaces have no meaning in JavaScript. So yes, they are the same. — Felix Kling
– Felix Kling, Commented Jan 4, 2017 at 17:50

Steve Thorpe · Accepted Answer · 2017-01-04 17:54:09Z

2

Your 'interpretations' are simply the removal of line feeds and white spaces. The results are functionally identical to the more readable, multi-line versions.

answered Jan 4, 2017 at 17:54

Steve Thorpe

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1 Comment

UtkarshPramodGupta Over a year ago

is my interpretation correct? because I don't really understand how multi-line code like those are parsed in JS. btw thanks for the reply :)

haltersweb · Accepted Answer · 2017-01-04 20:38:30Z

1

Your interpretation is correct but this coding style has nothing to do with ES6. It is simply part of the JS syntax.

Developers will often put chained methods onto separate lines to make what's happening to the target object clearer.

Read this article about method chaining and see the bottom of the article for an example of chained methods on different lines: https://schier.co/blog/2013/11/14/method-chaining-in-javascript.html

answered Jan 4, 2017 at 20:38

haltersweb

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2 Comments

UtkarshPramodGupta Over a year ago

is it correct even for the second one (new Q(value)...)?

haltersweb Over a year ago

Yes, even for the second one.

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