[Proto-Scripty] Re: Problem with prototype and arrays.
Hi, I'm missing something here. One of us is. :-) The OP's problem was that using for..in on an array was looping through the property names and he expected it to loop through array indexes. That's the common misconception I was talking about. People think for..in loops through array indexes, which is just plain wrong. While it *does* that (because array indexes are property names), it's not limited to doing that; it loops through all enumerable properties (as you know). All will appear to be well in a vanilla environment with a straightforward array instance, but not when either the Array.prototype or the array instance has had other enumerable properties added to it. I think if you read the wiki article[1] I pointed him at (I wrote it, a couple of years back) you'll see what I'm saying more clearly -- though since you clearly understand what for..in does, it may not be a worthwhile way to spend your time. The article is for people like the OP who aren't that familiar with JavaScript's arrays and the for..in construct. [1] http://proto-scripty.wikidot.com/prototype:tip-looping-through-arrays -- T.J. On Aug 3, 1:10 am, RobG rg...@iinet.net.au wrote: On Aug 3, 2:19 am, T.J. Crowder t...@crowdersoftware.com wrote: Hi, Yes, it's an extremely common misconception. What, that for..in iterates over an object's properties? No, that it loops over array indexes. I'm missing something here. Array indexes are properties, which is why they are included in for..in iteration. The OPs problem was how to deal with properties from the [[prototype]] chain, not that array properties were included in for..in. There are two issues to deal with when using for..in with a javascript array: 1. properties may have been added to Array.prototype, and 2. object properties are not guaranteed to be returned in any particular order Both the above are common to any use of for..in. Item 1 is easily dealt with. If order matters, a for, while or do loop can be used. Otherwise, there is no issue. -- Rob -- You received this message because you are subscribed to the Google Groups Prototype script.aculo.us group. To post to this group, send email to prototype-scriptacul...@googlegroups.com. To unsubscribe from this group, send email to prototype-scriptaculous+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/prototype-scriptaculous?hl=en.
[Proto-Scripty] Re: Problem with prototype and arrays.
On Aug 2, 3:43 pm, T.J. Crowder t...@crowdersoftware.com wrote: Hi, I found that array looping method online, I guess I will remove that page from my bookmarks. Yes, it's an extremely common misconception. What, that for..in iterates over an object's properties? It's per ECMA-262. There are strategies for dealing with properties on an array's internal prototype chain so that for..in works just fine, even when it's built-in prototype has been modified. -- Rob -- You received this message because you are subscribed to the Google Groups Prototype script.aculo.us group. To post to this group, send email to prototype-scriptacul...@googlegroups.com. To unsubscribe from this group, send email to prototype-scriptaculous+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/prototype-scriptaculous?hl=en.
[Proto-Scripty] Re: Problem with prototype and arrays.
Hi, Yes, it's an extremely common misconception. What, that for..in iterates over an object's properties? No, that it loops over array indexes. -- T.J. On Aug 2, 3:49 pm, RobG rg...@iinet.net.au wrote: On Aug 2, 3:43 pm, T.J. Crowder t...@crowdersoftware.com wrote: Hi, I found that array looping method online, I guess I will remove that page from my bookmarks. Yes, it's an extremely common misconception. What, that for..in iterates over an object's properties? It's per ECMA-262. There are strategies for dealing with properties on an array's internal prototype chain so that for..in works just fine, even when it's built-in prototype has been modified. -- Rob -- You received this message because you are subscribed to the Google Groups Prototype script.aculo.us group. To post to this group, send email to prototype-scriptacul...@googlegroups.com. To unsubscribe from this group, send email to prototype-scriptaculous+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/prototype-scriptaculous?hl=en.
[Proto-Scripty] Re: Problem with prototype and arrays.
On Aug 3, 2:19 am, T.J. Crowder t...@crowdersoftware.com wrote: Hi, Yes, it's an extremely common misconception. What, that for..in iterates over an object's properties? No, that it loops over array indexes. I'm missing something here. Array indexes are properties, which is why they are included in for..in iteration. The OPs problem was how to deal with properties from the [[prototype]] chain, not that array properties were included in for..in. There are two issues to deal with when using for..in with a javascript array: 1. properties may have been added to Array.prototype, and 2. object properties are not guaranteed to be returned in any particular order Both the above are common to any use of for..in. Item 1 is easily dealt with. If order matters, a for, while or do loop can be used. Otherwise, there is no issue. -- Rob -- You received this message because you are subscribed to the Google Groups Prototype script.aculo.us group. To post to this group, send email to prototype-scriptacul...@googlegroups.com. To unsubscribe from this group, send email to prototype-scriptaculous+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/prototype-scriptaculous?hl=en.
[Proto-Scripty] Re: Problem with prototype and arrays.
Hi, `for..in` is not for looping through the indexes of an array, it's for looping through the property names of an object. More in the API docs: http://api.prototypejs.org/language/array/ ...and in the unofficial wiki: http://proto-scripty.wikidot.com/prototype:tip-looping-through-arrays HTH, -- T.J. Crowder Independent Software Consultant tj / crowder software / com www.crowdersoftware.com On Jul 31, 1:44 pm, Rog ro...@aidreams.co.uk wrote: Hi there everyone, I am pretty new to javascript but do a lot of other programming. Something is not working as expected. Here's a bit of code I am testing : == html head script type=text/javascript src=prototype1-1-6.js/script /head script var smileySet = new Array(); smileySet['test'] = 'hello'; for (var smiley in smileySet) document.write(smiley + ' = ' + smileySet[smiley] + 'br /'); /script /html === If I run that I get a screen full of the prototype javascript functions. Without including prototype I just get the one array element 'test = hello' as expected. Why are all the prototype functions being added to the array ? Many thanks ! -- You received this message because you are subscribed to the Google Groups Prototype script.aculo.us group. To post to this group, send email to prototype-scriptacul...@googlegroups.com. To unsubscribe from this group, send email to prototype-scriptaculous+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/prototype-scriptaculous?hl=en.
[Proto-Scripty] Re: Problem with prototype and arrays.
Thanks very much, that makes a lot of sense now. I found that array looping method online, I guess I will remove that page from my bookmarks. Thanks for setting me right :) On 1 Aug, 11:47, T.J. Crowder t...@crowdersoftware.com wrote: Hi, `for..in` is not for looping through the indexes of an array, it's for looping through the property names of an object. More in the API docs: http://api.prototypejs.org/language/array/ ...and in the unofficial wiki: http://proto-scripty.wikidot.com/prototype:tip-looping-through-arrays HTH, -- T.J. Crowder Independent Software Consultant tj / crowder software / comwww.crowdersoftware.com -- You received this message because you are subscribed to the Google Groups Prototype script.aculo.us group. To post to this group, send email to prototype-scriptacul...@googlegroups.com. To unsubscribe from this group, send email to prototype-scriptaculous+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/prototype-scriptaculous?hl=en.
