Javascript quick variable assignment

Question

This is one of those questions I don't know how to properly word so I appologize if it has been asked before.

Python provides some very simple statements for quickly assigning arrays to values. For example if I have a box as an array like so box=[0,0,100,100] I can assign those points like so x1,y1,x2,y2=box. Is there such a statement in javascript? This would be especially useful in class functions where var x1,y1,x2,y2=this.box would be much less verbose than

var x1=this.box[0];
var y1=this.box[1];
var x2=this.box[2];
var y2=this.box[3];

If so, then are there any javascript methods that apply this to for loops? Coming from python, the below just seems so intuitive

boxes=[[0,0,100,100],[0,0,100,100],[0,0,100,100],[0,0,100,100]]

for box in boxes:
 x1,x2,x3,x4 = box
 #do something

definitely more intuitive than

var boxes=[[0,0,100,100],[0,0,100,100],[0,0,100,100],[0,0,100,100]];

    for (var i = 0; i < boxes.length : i++){
      var box = boxes[i];
      var x1 = box[0];
      var y1 = box[1];
      var x2 = box[2];
      var y2 = box[3];

FYI its call destructured assignment and in in js 1.7 (developer.mozilla.org/en/…) — Alex K.
– Alex K., Commented May 27, 2011 at 9:30
@Alex: Thanks. It's, in my opinion, not as clean as in Python, but it definitely helps — puk
– puk, Commented May 27, 2011 at 9:41
@Alex, another example is default values. I really could use default values in function parameters. — puk
– puk, Commented May 27, 2011 at 19:01

user578895 · Accepted Answer · 2011-05-27 09:19:30Z

4

Cross browser it isn't possible, sorry. Firefox implements a new syntax, but no other browser currently does:

var [x, y] = [1, 2];

answered May 27, 2011 at 9:19

user578895

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3 Comments

Exelian Over a year ago

This is new javascript syntax, as far as I know 1.7. Sadly the support isn't available.

puk Over a year ago

Such a pitty, this is one of the cases where I don't think JS has made a good design decision

user578895 Over a year ago

Note that plenty of people rave about coffeescript: jashkenas.github.com/coffee-script, which compiles down to JS. It supports the above syntax.

tiagoboldt · Accepted Answer · 2011-05-27 09:16:13Z

1

I believe that's a no go.. Alternatively, you could generate your list as

var boxes = [
   {'x1':0, 'y1':0, 'x2':100, 'y2':100},
   {'x1':0, 'y1':0, 'x2':100, 'y2':100},
   {'x1':0, 'y1':0, 'x2':100, 'y2':100},
]

Then you can access them with

for (i in boxes) {
   var box = boxes[i]
   // use box.x1 box.y1 box.x2 box.y2
   //such as:
   console.log(box.x1);
}

answered May 27, 2011 at 9:16

tiagoboldt

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