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Webmaster Forum / HTML, CSS, Scripts / JavaScript / February 2006Calculate field values using javascript
Please excuse me if I am posting in wrong NG. Can someone explain how I can use javascript (I am assuming this is the best way to do it) to add two field values together. I.e. field 1 plus field 2 equals field 3 (this is in a php form) Also how can I set a field to be a value depending on what the user selects, i.e. they may have eight items to select from and each one has a different value. The above javascript will then use that value to add to another field value to give a me a total value I know this should be simple and I am looking around and reading how to do this, but any pointers or sharable code would be helpful. Cheers Greg > Please excuse me if I am posting in wrong NG. > [quoted text clipped - 11 lines] > I know this should be simple and I am looking around and reading how to do > this, but any pointers or sharable code would be helpful. There are many examples at this website: http://www.w3schools.com/js/js_examples.asp some folks say the site has many errors - maybe so - but it also has many good examples. Take a look and decide for yourself. JRS: In article <74aMf.44599$bW.19883@bignews8.bellsouth.net>, dated Sat, 25 Feb 2006 23:27:39 remote, seen in news:comp.lang.javascript, Hal Rosser <hmrosser@bellsouth.net> posted : >> Can someone explain how I can use javascript (I am assuming this is the >best [quoted text clipped - 9 lines] >value >> to give a me a total value >There are many examples at this website: >http://www.w3schools.com/js/js_examples.asp >some folks say the site has many errors - maybe so - but it also has many >good examples. >Take a look and decide for yourself. If the OP knows as little as he asserts, he will not be able (with reasonable effort) to judge which parts, if any, are good. Actually, there are two ways of adding; if one adds "cat" and "fish" one gets "catfish", but if one adds 1 and 2 one gets 3. Javascript supports both of those, alas with the same operator. Generally, one wants to do more than the OP asks; hence a slightly more general solution will be more informative. Let ADDR stand for some way of addressing a field. Then ADDR.value is, for the sort of control in question, a String holding the content of the field. If that string represents a number, then +ADDR.value gives a Number of appropriate value. So: var Qty1 = +ADDR1.value var Qty2 = +ADDR2.value ADDR3.value = Qty1 + Qty2 // auto-converted to String For the second case, use selectedIndex to address the field chosen, like PlaceValue.value = + Places.options[Places.selectedIndex].value Read the newsgroup FAQ.  Signature© John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 IE 4 © <URL:http://www.jibbering.com/faq/> JL/RC: FAQ of news:comp.lang.javascript <URL:http://www.merlyn.demon.co.uk/js-index.htm> jscr maths, dates, sources. <URL:http://www.merlyn.demon.co.uk/> TP/BP/Delphi/jscr/&c, FAQ items, links. > So: var Qty1 = +ADDR1.value > var Qty2 = +ADDR2.value > ADDR3.value = Qty1 + Qty2 // auto-converted to String I preffer: +field.value || 0 Then, NaN values will be converted to 0 SignatureJonas Raoni Soares Silva http://www.jsfromhell.com JRS: In article <du10ih$tc6$4@emma.aioe.org>, dated Tue, 28 Feb 2006 05:10:57 remote, seen in news:comp.lang.javascript, Jonas Raoni <jonasraoni@gmail.com> posted : >> So: var Qty1 = +ADDR1.value >> var Qty2 = +ADDR2.value [quoted text clipped - 5 lines] > >Then, NaN values will be converted to 0 In general, NaN values should not be converted to zero; they should result in a form of error message suited to the application. Signature© John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 IE 4 © <URL:http://www.jibbering.com/faq/> JL/RC: FAQ of news:comp.lang.javascript <URL:http://www.merlyn.demon.co.uk/js-index.htm> jscr maths, dates, sources. <URL:http://www.merlyn.demon.co.uk/> TP/BP/Delphi/jscr/&c, FAQ items, links. > JRS: In article <74aMf.44599$bW.19883@bignews8.bellsouth.net>, dated > Sat, 25 Feb 2006 23:27:39 remote, seen in news:comp.lang.javascript, Hal [quoted text clipped - 46 lines] > > Read the newsgroup FAQ. OP here Thanks and yes VERY new to this cheers for your help Greg |
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