a simple javascript function needed

@cofactorFeb 09.2010

I need a simple javascript function f(z) which does the following.

for z=3,4 —> output =1
for z=5,6 —> output =2
for z=7,8 —> output =3
for z=9,10 —> output =4
for z=11,12 —> output =5
for z=13,14 —> output =6
for z=15,16 —> output =7

There is no other value of z than given above..

Can you please help ? how do I write this function ?

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JavaScript

@Gozzy82Feb 09.2010 — #this should be it..

<i>
 </i>&lt;script type="text/javascript"&gt;
 function f(z){
 var ret;
 switch(z){
 case "3,4": ret = 1; break;
 case "5,6": ret = 2; break;
 case "7,8": ret = 3; break;
 case "9,10": ret = 4; break;
 case "11,12": ret = 5; break;
 case "13,14": ret = 6; break;
 case "15,16": ret = 7; break;
 default: ret = 0; break;
 }
 return ret;
 }
 /* uncomment this to test the function 
 window.onload  = function(){
 alert( f('11,12') );
 }
 */
 &lt;/script&gt;

@rpg2009Feb 09.2010 — #Got a little silly with the ands(&&)

[CODE]function f(z){
 var x = z.match(/^(dd?),(dd?)$/);
 return (x && (x[1]==x[2]-1) && (x[2]<17 && x[2]>3) && !(x[2]%2))?x[2]/2-1:"invalid entry";
 }[/CODE]

Output examples

[CODE]alert (f('2,3')); //invalid entry
 alert (f('3,4')); //1
 alert (f('15,16')); //7
 alert (f('17,18')); //invalid entry
 alert (f('3,6')); //invalid entry
 alert (f('6,7')); //invalid entry
 alert (f('9,10')); //4
 alert (f('a,b')); //invalid entry[/CODE]

RLM

@rpg2009Feb 10.2010 — #I need a [B]simple[/B] javascript function[/QUOTE]

Given the question and a bit of hindsight. A breakdown.

var x = z.match(/^{^[B]([/B]dd?[B])[/B],[B]([/B]dd?[B])[/B]$/);}

The regex

[CODE]/^   begins with
 (   capture this
 d   number between 0-9
 x?   match x 0 or 1 times
 so dd? means a single or double digit number. d{1,2} does the same.
 )   end of capture
 escapes and , means match a comma
 (dd?)   capture second single or double digit number
 $/   ends with
 ()'s or back-references capture the matches in an array. In this case x[1] is the first (match) and x[2] the second (match).
 
 so if z = '3,4' the match returns x[1] = 3 and x[2] = 4[/CODE]

the condition

[CODE]
 x && (x[1]==x[2]-1) && (x[2]<17 && x[2]>3) && !(x[2]&#37;2)
 
 x   is there a match at all?
 x[1]==x[2]-1   does the first number equal the second-1?
 x[2]<17 && x[2]>3   does the second number fall between 3 and 17?
 !(x[2]%2)   is 2 a factor of the second number or in other words is x[2] an even number?
 [/CODE]

[CODE]?x[2]/2-1   if that matches, return the second number divided by 2 and take away 1
 : "invalid entry";   else return invalid.[/CODE]

I'm sure this could be improved on using better or simpler logic, but thought a breakdown may be helpful.

RPG

a simple javascript function needed

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