iterate over an array and sum up all values with JS

Question

as the title says i'm trying to sum up using a for loop to iterate over an array. can you give me some pointers as to where i'm going wrong here. i am returning the value NaN.

var total = 0;

function sum(input) {
    for (idx=0; idx<=input; idx++) {
        total += input[idx];
    }
    return total;
}

Solution 1

You are using input both as an integer, and as an array of values. Probably you mean for( var idx = 0; idx < input.length; ++idx )....

Solution 2

You actually don't need a loop to do this in modern browsers, you can use the Array.reduce function:

var sum = input.reduce(function(a,b){
    return a+b;
}, 0);

Solution 3

variable total is not declared!

function sum(input) {
    var total = 0;
    for (idx=0; idx <= input.length; idx++) {
        total += input[idx];
    }
    return total;
}

Comments

[xtofl]

It seems declared to me. Only it's global, so the results will always grow.

[danny white]

ahh thanks very much .. thats where i was going wrong .. this has sorted it now thanks very much

[xtofl]

nice functional style - not very newbie-friendly, though.

[xtofl]

@dannywhite: be sure to take the other answers into account, too: your total is globally scoped.