Javascript dealing with unkown number of function arguments

Question

My function needs to accept any number of lists, then output their symmetric difference. sym([1, 2, 3], [5, 2, 1, 4]) should return [3, 5, 4] and sym([1, 2, 5], [2, 3, 5], [3, 4, 5]) should return [1, 4, 5]. How can I deal with the unknown number of arguments? I thought that I could use the single variable args to create a list of lists, but that isn't working.

function isin(num,arra)
{
  for (i=0; i<arra.length; i++)
  {
    if (num == arra[i]){return true;}
  }
  return false;
}

function sym(args) {
   var syms = [];
   console.log(args);
   for (i=0; i<args.length; i++)
   {
     var ins = false;
     for (j=0; j<args[i].length; j++)
     {
       for (k=i+1; k < args.length; k++)
       {
         if(isin(args[i][j], args[k]))
         {
           ins = true;
         }
       }
     }
     if (ins === false)
     {
       syms.push(args[i][j]);
     }
   }
  return syms;
}
sym([1, 2, 3], [5, 2, 1, 4]);

I need to pass the lists as multiple arguments – kilojoules Jan 04 '16 at 01:06 — kilojoules, Jan 04 '16 at 01:06

score 1 · Accepted Answer · answered Jan 04 '16 at 00:59

use arguments, not args

and you dont need to have it in the function definition.

(note: Im assuming the rest of your code works once you actually get what youre expecting passed in)

so:

function sym() {
   var syms = [];
   console.log(arguments);
   for (i=0; i<argumentss.length; i++)
   {
     var ins = false;
     for (j=0; j<arguments[i].length; j++)
     {
       for (k=i+1; k < arguments.length; k++)
       {
         if(isin(arguments[i][j], arguments[k]))
         {
           ins = true;
         }
       }
     }
     if (ins === false)
     {
       syms.push(arguments[i][j]);
     }
   }
  return syms;
}

Qwertiy · Answer 2 · 2016-01-04T01:16:18.650

1

For arrays with numbers:

function sym() {
  var temp = {}, res = [];

  for (var q=0; q<arguments.length; ++q) {
    for (var w=0; w<arguments[q].length; ++w) {
      temp[arguments[q][w]] ^= 1;
    }
  }

  for (var key in temp) {
    if (temp[key] === 1) {
      res.push(+key);
    }
  }

  return res;
}

console.log(sym([1, 2, 3], [5, 2, 1, 4]), sym([1, 2, 5], [2, 3, 5], [3, 4, 5]))

edited Jan 04 '16 at 01:16

answered Jan 04 '16 at 01:04

Qwertiy

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why do you use the XOR `^`? – kilojoules Jan 04 '16 at 01:09
@kilojoules, because number should be contained in odd number of arrays as I undertand. Also bitwise operation will convert nonexisting field to 0. – Qwertiy Jan 04 '16 at 01:11

score 1 · Answer 3 · answered Jan 04 '16 at 01:22

1

Es6 introduces rest paramters. You can use it instead of arguments object.

function logAllArguments(...args) {
    for (var arg of args) {
        console.log(arg);
    }
}

logAllArguments(1,2,3)

answered Jan 04 '16 at 01:22

blessanm86

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score 0 · Answer 4 · answered Jan 04 '16 at 00:59

0

Within in each function scope you have access to the arguments object . Any parameters you pass in will available inside of it. You can convert the arguments object to an array using Array.prototype.slice.apply(null,arguments) , and iterate over it.

answered Jan 04 '16 at 00:59

Michael Sova

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Javascript dealing with unkown number of function arguments

4 Answers4