Disallow Use of Chained Assignment Expressions (no-multi-assign)

[feross]

This rule disallows using multiple assignments within a single statement.

http://eslint.org/docs/rules/no-multi-assign

var a = b = c = 5 // avoid

var a = 5  // ok
var b = a
var c = a

Rule:

no-multi-assign: "error"

[dcousens]

var a = 5  // ok
var b = a
var c = a

Is probably more likely for the 'correct' example

[feross]

@dcousens Yep, you're right. Updated the example.

[feross]

This rule fails in 34 repos, and prevents a bit more than I'm comfortable with. For example:

exports.no = exports.noCase = require('no-case')
exports.dot = exports.dotCase = require('dot-case')

exports.randomBytes = exports.rng = exports.pseudoRandomBytes = exports.prng = require('randombytes')

self.readable = self.writable = false

self.socket = socketPool[self.announceUrl] = new Socket(self.announceUrl)

These all seem fine to me, so thinking we should skip this rule. Thoughts?

[timoxley]

I don't see many negatives of allowing multiple assignments on one line. I use it often like in @feross's example above. I think it's good for condensing low value noise onto a single line.

[timoxley]

For similar reasons I often lament standard including the "no return assignment" rule, but I do appreciate the danger of accidentally returning an assignment when you meant a conditional. Not sure this pattern suffers from that risk as much. Vote skip.

[dcousens]

For me, this is purely a readability issue, and the only class of bugs it could relate to is:

var x = 1
var y = x = 2

instead of x + 2.
I don't think I can recall a time that has happened to me though.

[feross]

Agree, it's mainly a readability issue and not a source of bugs. And it prevents valid code that we don't want to rewrite, like multiple exports on one line.