madsovenielsen Posted August 13, 2009 Share Posted August 13, 2009 Hello all.Im having a hard time understanding function parameters. what are the applications for it. and how does it work ? function helloworld(string){ return "hello world";} I know theres probably some place i can find it. but im hoping one from the forum can explain it to me. /mads Link to comment Share on other sites More sharing options...
ckrudelux Posted August 13, 2009 Share Posted August 13, 2009 Hello all.Im having a hard time understanding function parameters. what are the applications for it. and how does it work ?function helloworld(string){ return "hello world";} I know theres probably some place i can find it. but im hoping one from the forum can explain it to me. /mads function writeGreatings(justAname){document.write("Hello" justAname);}var user = "Carl";writeGreatings(user);output:Hello Carl hope this helps. And correct me if I'm wrong. Link to comment Share on other sites More sharing options...
packrat Posted August 13, 2009 Share Posted August 13, 2009 You should probably read the JavaScript tutorialhttp://www.w3schools.com/js/default.aspa few times over and run through some of the 'try it yourself' examples.The short answer is that a function parameter is an input variable, some value you pass to a function that the function may then act upon.When you alert('hello world!'); 'hello world!' is the parameter you are passing to the alert() function.Practice makes for better understanding. Link to comment Share on other sites More sharing options...
madsovenielsen Posted August 13, 2009 Author Share Posted August 13, 2009 function writeGreatings(justAname){document.write("Hello" justAname);}var user = "Carl";writeGreatings(user);output:Hello Carl hope this helps. And correct me if I'm wrong. Yes. but im still not sure i understand the benefits. i mean you can get the exact same result with a variable. Link to comment Share on other sites More sharing options...
madsovenielsen Posted August 13, 2009 Author Share Posted August 13, 2009 Ahh.. okay. so i can use variables as function parameters ? Link to comment Share on other sites More sharing options...
justsomeguy Posted August 13, 2009 Share Posted August 13, 2009 You can use anything as a function parameter. You can send a function as a parameter to another function. You can send objects, arrays, functions, events, regular variables, constants, etc. The reason you use parameters is so that you can build a function that you can use in several situations. You can only use this function in one situation, to show an error that they need to fill out a username: function show_error(){ alert('Username is empty');} That's not very useful. If you send the text as a parameter then you can use it to show anything: function show_error(txt){ alert(txt);} Granted, a function that just calls alert isn't very useful, but you should get the idea.Maybe an add function is more useful: function add(a, b){ return a + b;} Link to comment Share on other sites More sharing options...
madsovenielsen Posted August 13, 2009 Author Share Posted August 13, 2009 Okay. how does one go about sending parameters to a function ? Link to comment Share on other sites More sharing options...
justsomeguy Posted August 13, 2009 Share Posted August 13, 2009 When you call a function you write parentheses after the name, parameters go in the parentheses. The alert function takes 1 parameter: // send constantalert('text');// send variablevar txt = 'show this';alert(txt);// send return value from another functionfunction get_text(){ return 'some text';}alert(get_text());// send value of an expressionalert(1 + 2);alert(typeof window.document);alert(typeof document.getElementById);alert(1 + 2 == 3); Link to comment Share on other sites More sharing options...
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