Define a function that contains an unknown function in javascript

Question

i was asked to define a function reduce, that has three parameters, an array, an unknown function, and a number, and reduces the array into a number

and this is was i was given before i was asked to define the function

reduce([1, 2, 3], function(total, number) {

    return total + number;

}, 0); // should return 6

I am a bit clueless on what this is asking me to do to be completely honest

if i could at least get some guideline id be grateful

here is my attempt

var reduce = function(array, func, initial){ 

    function func(){
}

    for( var i = 0; i < array.length; i++){

        func(initial, array[i]);
    }
}

sounds like you're being asked to create Array.prototype.reduce as a static method. — zzzzBov
– zzzzBov, Commented Nov 14, 2013 at 5:21

2 revs · Accepted Answer · 2013-11-14 07:39:39Z

1

Try:

function reduce(list, f, acc) {
    return list.length ?
        reduce(list.slice(1), f, f(acc, list[0])) :
        acc;
}

Simple.

edited Nov 14, 2013 at 7:39

community wiki

2 revs
Aadit M Shah

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Comments

Alphadelta14 · Accepted Answer · 2013-11-14 05:28:50Z

0

You need to be sure to create a total variable which will be redefined after every function call. You were very close. Try this out:

var reduce = function(array, func, initial){
    var total = initial,
        arr_len = array.length;
    for(var i = 0; i < arr_len; i++){
        total = func(total, array[i]);
    }
};

answered Nov 14, 2013 at 5:28

Alphadelta14

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2 Comments

Eugene Choi Over a year ago

ha, i think this is what the question was aiming towards. i guess i did not realize how to formulate an unknown function to be called each time. in the exemplary expression above, is total+number representing the parameter function?

Alphadelta14 Over a year ago

Yes. The function takes the current state, total, and changes that state with the current argument of the array (number above). The function you used just increments total.

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