'Length' Property Undefined while iterating Array

Question

Iterating an array to find the longest string. Each time I\'ve received the error Cannot read property length of undefined. Console.log tells me th

Answer 1

Instead of error prone hand-written loops for iterating over an array, why not take advantage of the functions that JS provides you - in this case Array.prototype.map:

function findLongestWord(s) {
    return Math.max.apply(this, s.split(/\s+/).map(function(w) {
        return w.length;
    }));
}

The Math.max.apply(this, some_array) is the standard JS way of calling Math.max(a, b, c, d, ...) with the given array instead of passing a list of parameters of unknown length.

In ES2015 you could use the even shorter:

function findLongestWord(s) {
    return Math.max(...s.split(/\s+/).map((w) => w.length));
}

Answer 2

You read error wrong :-) not length is undefined, but object where you try get this property - undefined.
So currentWord is undefined
because you have wrong loop condition: i<=arrayL,
when i == arrayL - var currentWord = array[i] is undefined and you get error.

Just fix it: i < arrayL

Answer 3

The problem is the bounds of your iteration

for (i=0; i<=arrayL; i++) {

Note that you are going to be looking for array[array.length] doing this and that will always be undefined because the 10th item in an array of 10 items is [9], [10] is undefined.

Also, please use var here

for (var i=0; i < arrayL; i++) {