In JavaScript, is chained assignment okay?

user_312716 0
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Am not new to JS or its syntax, but sometimes, the semantics of the language has me stumped at times. At work today, a colleague mentioned this:

var a = b = [];

is not the same as

var a = [], b = [];

or

var a = []; var b = [];

since the first version actually assigns the reference to an empty array to a and b. I couldn't quite accept this as true, but I'm not sure. What do you all think?

variable-assignment object javascript
6 Answers

To complement the already provided answers. ref assignments are different from value assignments

var x = y = 3; // by value
y++; // 4
x; // 3

var a = b = []; // by ref
b.push(1); // [1];
a; // [1]
a = [];
a.push(2); // [2];
b; // [1]

Now that we've addressed 2 two, your question also makes reference to linting, which is the practice of "pretty code" (not functional). In fact, JSHint has deprecated all their "pretty code rules"

That been said, I usually use the following style.-

var a, b, c, // first row all unassigned
    x = 1, // 1 row per assigned
    y = 2,
    list = [
       'additional',
       'indentation'
    ],
    obj = {
       A: 'A',
       B: 'B'
    };
var z = y +2; // created a new `var` cluster since it uses a var from the previous
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