Counting elements in an array and comparing them, javascript

Question

I'm trying to solve a problem using my very limited knowledge of Javascript.

I've tried to build a way to count the number of times a particular letter appears in an array and compare it to the number of times another letter appears in the same array.

I'm able to pass 3 out 4 tests and have re written the code many times trying as many methods as I know.

I realize that what I've done is not efficient...just working on problem solving with a weeks worth of skills.

Appreciate any input. Thanks.

function isValidWalk(walk) {
 var north = new Object ();
 var south = new Object ();
 var east = new Object ();
 var west = new Object ();
for (var i = 0; i <walk.length; i++){
if (walk[i] == "n")
{north.input = "x"}
}
for (var i = 0; i <walk.length; i++){
if (walk[i] == "s")
{south.input = "x"} 
}
for (var i = 0; i <walk.length; i++){
if (walk[i] == "e")
{east.input = "x"} 
}
for (var i = 0; i <walk.length; i++){
if (walk[i] == "w")
{west.input = "x"} 
}



if (north.input == south.input && east.input == west.input && walk.length==10) {
return true;
}
else {
return false;
}
}

One thing that comes immediatly to mind: why all these `for` loops, when you could use just one, and do all your tests inside of it? — blex, Apr 03 '16 at 17:45
You don't need multiple loops. Just use one with `switch(walk[i])` instead. — Andy, Apr 03 '16 at 17:46
Test.expect(!isValidWalk(['n','n','n','s','n','s','n','s','n','s']), 'should return false'); — 736f5f6163636f756e74, Apr 03 '16 at 17:48
This is just the latest version. I originally had just one loop with else if statements but was still failing the test. — 736f5f6163636f756e74, Apr 03 '16 at 17:49

blex · Accepted Answer · 2016-04-03T18:09:02.587

0

Here is how I would do it:

function isValidWalk(walk) {
    var steps = {n: 0, s: 0, e: 0, w: 0};

    for (var i=0, l=walk.length; i<l; i++) {
        if (steps.hasOwnProperty(walk[i])) {
            steps[walk[i]]++;
        } else {
            return false; // The element is not "n","s","e", or "w"
        }
    }

    return (steps.n == steps.s && steps.e == steps.w && walk.length == 10);
}

console.log( isValidWalk(['n','n','n','s','n','s','n','s','n','s']) );   // returns false
console.log( isValidWalk(['n','n','n','s','s','s','n','s']) );           // returns false
console.log( isValidWalk(['n','gg','hh','s','s','s','n','s','n','n']) ); // returns false
console.log( isValidWalk(['n','n','n','s','s','s','n','s','n','s']) );   // returns true

edited Apr 03 '16 at 18:09

answered Apr 03 '16 at 17:51

blex

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please do not use `for ... in` for arrays. – Nina Scholz Apr 03 '16 at 18:06
1

@NinaScholz Alright, I've changed it. – blex Apr 03 '16 at 18:09
Thank you for this. I also re-wrote using switch and both versions passed. Plus I learned about the hasOwnProperty method. – 736f5f6163636f756e74 Apr 03 '16 at 18:33

Counting elements in an array and comparing them, javascript

1 Answers1