How to create an object with an unknown number of arguments in javascript?

Question

Well, I have to create an object that represents an polynom af any size:

var polynom = function() {
    //code ...
};
p1 = polynom(1,6,3,4); // 1x^6 + 3x^4
p2 = polynom(3,5,2,1,7,3); // 3x^5 + 2x^1 + 7x^3

what I want to do is write a method that return an array with all these arguments. I read a little about this.arguments, so I write something like that:

var polynom = function() {

    getArguments = function() {
    array = [];
    for(var i = 0; i < this.arguments.size; i++) array.push(this.arguments[i]);
    return array;
  }
};

const p1 = new polynom(3,2);
console.log(p1.getArguments());

and I get this message

TypeError: Cannot read property 'getArguments' of undefined
    at eval:14:16
    at eval
    at new Promise

I'm new at javascript so sorry if there's something wrong, but I would appreciate some help to write this method.

const p1 = new polynom(3,2); ... your polynom object does nothing with it's arguments, so, they're lost — Jaromanda X
– Jaromanda X, Commented Nov 30, 2017 at 2:38
you just write "this" before all the function? I did this but still the same error — Ramon Fragoso
– Ramon Fragoso, Commented Nov 30, 2017 at 2:39
A simpler way to get function arguments as an array: [].prototype.slice.call(arguments); — fubar
– fubar, Commented Nov 30, 2017 at 2:40

Jeremy Myers · Accepted Answer · 2017-11-30 02:44:03Z

1

What you are looking for is Rest arguments.

var polynom = function(...args) {
  this.getArguments = function() {
    var array = [];
    for(var i = 0; i < args.length; i++) {array.push(args[i]);};
    return array;
  }
};

const p1 = new polynom(3,2);
console.log(p1.getArguments());

answered Nov 30, 2017 at 2:44

Jeremy Myers

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7 Comments

user8897421 Over a year ago

You don't need the loop. The args is already an Array. Just return it, or .slice() it if you want a shallow copy.

Jaromanda X Over a year ago

... isn't available in all browsers (I'm calling you out, Internet Exploder)

Ramon Fragoso Over a year ago

But @rockstar is right, args is already an array, thank you too man.

Jaromanda X Over a year ago

if you're going to use ES2016+ ... use all of it

class polynom {     constructor(...args) {         this.args = args;     }     getArguments() {         return this.args;     } };

Jaromanda X Over a year ago

for Internet Exploder -

function polynom() {     this.args = [].slice.call(arguments); } polynom.prototype.getArguments = function() {     return this.args; };

- this is all JavaScript 101 stuff!

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