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Webmaster Forum / HTML, CSS, Scripts / JavaScript / May 2007Variable variables stored in an array and called == problem.
I am missing something fundamental here. I have an array: arr1 = ['one', 'two', 'three']; I have three functions named one, two, and three. Is it possible to use arr1[0]();? (Or something like it, since that is obviously not the correct method.)  Signature-Lost Remove the extra words to reply by e-mail. Don't e-mail me. I am kidding. No I am not. -Lost wrote on 27 mei 2007 in comp.lang.javascript: > I am missing something fundamental here. > [quoted text clipped - 6 lines] > Is it possible to use arr1[0]();? (Or something like it, since that is > obviously not the correct method.) <script type='text/javascript'> var arr = ['one', 'two', 'three']; function one(){ alert('-ONE-'); }; window[arr[0]](); </script> SignatureEvertjan. The Netherlands. (Please change the x'es to dots in my emailaddress) >-Lost wrote on 27 mei 2007 in comp.lang.javascript: > [quoted text clipped - 20 lines] > ></script> Yes. But. The OP hasn't said that one, two, and three are *global* functions. We are just guessing that they are. The OP hasn't said that the code is running in a browser, and so has a window variable. We are just guessing that it has. The OP hasn't said if the code can run inside a 'with' statement and whether the function names are allowed to be captured by the 'with' object. We are just guessing that they aren't. To make 'arr[0]' do exactly what writing 'one' would have done you need to use 'eval'. Since this is evil we need to know what the OP is trying to do : there might be a better way. John SignatureJohn Harris John G Harris said the following on 5/28/2007 3:28 PM: >> -Lost wrote on 27 mei 2007 in comp.lang.javascript: >> [quoted text clipped - 25 lines] > The OP hasn't said that one, two, and three are *global* functions. We > are just guessing that they are. Considering that they asked how to execute that function though, it is pretty reasonable to assume they are global functions. > The OP hasn't said that the code is running in a browser, and so has a > window variable. We are just guessing that it has. The default, here - unless stated otherwise -, is that it is running in a browser. > The OP hasn't said if the code can run inside a 'with' statement and > whether the function names are allowed to be captured by the 'with' > object. We are just guessing that they aren't. And whether it can or not is irrelevant. > To make 'arr[0]' do exactly what writing 'one' would have done you need > to use 'eval'. I flat don't believe that. In fact, I know it isn't true. SignatureRandy Chance Favors The Prepared Mind comp.lang.javascript FAQ - http://jibbering.com/faq/index.html Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/ >John G Harris said the following on 5/28/2007 3:28 PM: <snip> >> To make 'arr[0]' do exactly what writing 'one' would have done you need >> to use 'eval'. > >I flat don't believe that. In fact, I know it isn't true. The following code alerts 'Local!', 'Local!', 'Global!'. How do you alter the window[... part to make it alert 'Local!', 'Local!', 'Local!'? <SCRIPT type="text/javascript"> var arr = ['one', 'two', 'three']; function one() { alert("Global!"); } var x = new Object(); x.one = function() { alert("Local!"); } with (x) { one(); eval( arr[0] + "()"); window[arr[0]](); } </SCRIPT> Oh, I forgot to say : it's copy-and-paste code that knows nothing about x, not even its name. John SignatureJohn Harris John G Harris said the following on 5/29/2007 4:32 PM: >> John G Harris said the following on 5/28/2007 3:28 PM: > [quoted text clipped - 5 lines] > The following code alerts 'Local!', 'Local!', 'Global!'. How do you > alter the window[... part to make it alert 'Local!', 'Local!', 'Local!'? First, I would alter it not to use "with" <URL: http://www.javascripttoolbox.com/bestpractices/#with> because of scope chain issues while using the "with" operator. Aside from that, I would have to tinker with it. And I would probably end up being inclined to believe it to be a legitimate use of eval and add it to my list. Interesting code to say the least. SignatureRandy Chance Favors The Prepared Mind comp.lang.javascript FAQ - http://jibbering.com/faq/index.html Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/ > -Lost wrote on 27 mei 2007 in comp.lang.javascript: > [quoted text clipped - 20 lines] > > </script> Many thanks. Out of all the replies, this is what I was looking for. Signature-Lost Remove the extra words to reply by e-mail. Don't e-mail me. I am kidding. No I am not. > I am missing something fundamental here. > [quoted text clipped - 11 lines] > Remove the extra words to reply by e-mail. Don't e-mail me. I am > kidding. No I am not. If that's really what you need, then eval( arr1[0] + "()" ); // not tested Darko wrote on 27 mei 2007 in comp.lang.javascript: >> I am missing something fundamental here. >> [quoted text clipped - 15 lines] > eval( arr1[0] + "()" ); > // not tested eval() is evil and not necessary here, see my other post for a better solution. SignatureEvertjan. The Netherlands. (Please change the x'es to dots in my emailaddress) Evertjan. a écrit : > eval() is evil and not necessary here, > see my other post for a better solution. Don't know if that answer to the question, but in addition this works : arr[0] = function () { one(); } arr[0](); SignatureStephane Moriaux et son (moins) vieux Mac déjà dépassé Stephane Moriaux and his (less) old Mac already out of date ASM wrote on 27 mei 2007 in comp.lang.javascript: > Evertjan. a écrit : >> [quoted text clipped - 5 lines] > arr[0] = function () { one(); } > arr[0](); It is not, please read the OQ. SignatureEvertjan. The Netherlands. (Please change the x'es to dots in my emailaddress) > Don't know if that answer to the question, but in addition this works : > > arr[0] = function () { one(); } > arr[0](); Thanks, but I did not wish to store functions as array entries to reduce overhead. Signature-Lost Remove the extra words to reply by e-mail. Don't e-mail me. I am kidding. No I am not. >> I am missing something fundamental here. >> [quoted text clipped - 15 lines] > eval( arr1[0] + "()" ); > // not tested I do not subscribe to the whole "eval() is evil" (although it is widely misused and abused in general), but this is certainly not adequate. Thank you though. Signature-Lost Remove the extra words to reply by e-mail. Don't e-mail me. I am kidding. No I am not. In comp.lang.javascript message <QbSdnUnM1t2KWMTbnZ2dnUVZ_rCsnZ2d@comcas t.com>, Sun, 27 May 2007 13:52:33, -Lost <maventheextrawords@techie.com> posted: >I have an array: > [quoted text clipped - 4 lines] >Is it possible to use arr1[0]();? (Or something like it, since that is >obviously not the correct method.) function one() { alert(1) } function two() { alert(2) } function six() { alert(6) } arr1 = [one, two, six] arr1[1]() // alerts 2 may be useful to you, unless you are obliged to use an array of strings. Signature(c) John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v6.05 IE 6. Web <URL:http://www.merlyn.demon.co.uk/> - w. FAQish topics, links, acronyms PAS EXE etc : <URL:http://www.merlyn.demon.co.uk/programs/> - see 00index.htm Dates - miscdate.htm moredate.htm js-dates.htm pas-time.htm critdate.htm etc. > In comp.lang.javascript message <QbSdnUnM1t2KWMTbnZ2dnUVZ_rCsnZ2d@comcas > t.com>, Sun, 27 May 2007 13:52:33, -Lost <maventheextrawords@techie.com> [quoted text clipped - 18 lines] > > may be useful to you, unless you are obliged to use an array of strings. I did wish to work under the constraints of string entries. The actual reason I wanted an array of strings as opposed to an array of functions was because of additional overhead. Signature-Lost Remove the extra words to reply by e-mail. Don't e-mail me. I am kidding. No I am not. |
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