Why am I getting this 'cannot read property 'length' of undefined'? (JavaScript)

Question

Granted it's the end of a long week and my brain's fried, but I'm at my wit's end with this. Why on earth am I getting this error with respect to options.length when it's a function parameter and it was passed in an array argument (assortment)?

(I'm trying to come up with a recursive solution to provide permutations (repetitions allowed) of an assortment of characters in an array)

var n = 10;
var assortment = ['a','b','c','d','e'];
console.log(permutations(n, assortment));

function permutations (num, options) {
    var solutions = [];
    var singleSet = [];
    if (singleSet.length === num) {
        solutions.push(singleSet);
        return;
    } else {
        for (var i=0; i < options.length; i++) {
            singleSet = singleSet.concat(permutations(options[i]));
        }
    }
    return solutions;
}

Where is the part where permutations (num, options) is called? — NewToJS
– NewToJS, Commented May 24, 2015 at 1:40

aquinas · Accepted Answer · 2015-05-24 01:40:20Z

3

You only pass one argument here:

    singleSet = singleSet.concat(permutations(options[i]));

answered May 24, 2015 at 1:40

aquinas

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3 Comments

zahabba Over a year ago

You're right and thank you. I added something (num) for the first argument and that error disappeared. Still puzzled why the error was registering for options.length in the for loop instead.

connexo Over a year ago

That is because for Javascript functions you cannot make a fixed definition as of how many parameters have to be passed to it.

aquinas Over a year ago

Because that's the first time you reference options. And options is undefined...cause you never passed it in :)

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