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make the `new` operator optional before the `JSZip` constructor #93

merged 3 commits into from Feb 13, 2014


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Mithgol commented Feb 11, 2014

As @qlqllu has reported, an attempt to shorten JSZip call (giving it the form var jsZIP = new require('jszip')()) fails.

The failure's cause is a well-known JavaScript's operator precedence (the operator new has higher precedence than a function call — even if Node's require is that function). However, frankly speaking, that precedence in this case looks counter-intuitive to me as well.

This case reminded me of John Resig's self-calling constructor pattern (given in Resig's blog entry Simple “Class” Instantiation in 2007). Nobody uses new $ with Resig's jQuery and, I think, JSZip might follow jQuery's example and benefit from it.

This pull request makes the new operator optional before JSZip's constructor. Programmers might continue using new or omit it, depending on their inner personal preferences:

  • not typing four characters (new + space) might feel more RAD and less boilerplate code;
  • typing new might serve as a reminder that a constructor call is ahead;
  • using someZIP = require('jszip')() instead of someZIP = new (require('jszip'))() means less brackets;
  • etc.

(Unlike the example in Resig's blog, this pull request refrains from using arguments.callee because the use of that property is believed to slow down the engine.)

This change introduces a new backwards-compatible feature. An npm publish of a new minor version is recommended.

@Mithgol Mithgol referenced this pull request Feb 11, 2014


compress .gif file error #89


dduponchel commented Feb 12, 2014

@Mithgol Nice ! Could you add an unit test for this constructor ? We already have one for current constructor. And I agree with you, this leads to a new minor version.

@Stuk should I prepare a v2.1.1 (with only #91) first / in parallel ? I think #91 is a bit urgent (as the installation fails behind a restrictive firewall) but we could wait to have more stuff for the v2.2.0. What do you think of it ?


Stuk commented Feb 12, 2014

@dduponchel a quick v2.1.1 with #91 sounds good to me


dduponchel commented Feb 12, 2014

I'm preparing it !

qlqllu commented Feb 13, 2014

I can see the version 2.1.1 in npm registry. I have tested it, it works great!


Mithgol commented Feb 13, 2014

I've just added a test; it passed on Travis CI.

@Stuk Stuk and 1 other commented on an outdated diff Feb 13, 2014

@@ -59,6 +59,9 @@ test("JSZip", function(){
var zip = new JSZip();
ok(zip, "Constructor works");
+ var zipNoNew = JSZip();
+ ok(zipNoNew.file, "Constructor adds `new` before itself where necessary");

Stuk Feb 13, 2014


I think these tests would be more explicit if changed to ok(zip instanceof JSZip, ...). Would you mind doing that?


Mithgol Feb 13, 2014



@Stuk Stuk added a commit that referenced this pull request Feb 13, 2014

@Stuk Stuk Merge pull request #93 from Mithgol/patch-1
make the `new` operator optional before the `JSZip` constructor

@Stuk Stuk merged commit a336db3 into Stuk:master Feb 13, 2014

1 check passed

default The Travis CI build passed

@Mithgol Mithgol referenced this pull request Feb 21, 2014


Update documentation #101

@dduponchel dduponchel added a commit to dduponchel/jszip that referenced this pull request Feb 22, 2014

@dduponchel dduponchel documentation about the optional `new` operator
See #93 for more informations.
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