JavaScript Function causing loop to end?

Question

I am having a problem with my function and loop and not sure why.

var a = ['1,0,1', '0,1,0', '1,1,1'];
var b = [1, 1, 1];

function myFunction() {
  for (i = 0; i < a.length; i++) {
    var user = a[i].split(',');
    var cs = cosinesim(user, b);
    document.getElementById("cs").innerHTML += String(user) + '  ' + String(cs) + '<br>';
    cs = 0;
    user = '';
  }
}

function cosinesim(A, B) {
  var dotproduct = 0;
  var mA = 0;
  var mB = 0;
  for (i = 0; i < A.length; i++) {
    dotproduct += (parseInt(A[i]) * parseInt(B[i]));
    mA += (parseInt(A[i]) * parseInt(A[i]));
    mB += (parseInt(B[i]) * parseInt(B[i]));
  }
  mA = Math.sqrt(mA);
  mB = Math.sqrt(mB);
  if ((mA * mB) == 0) {
    var similarity = 0
  } else {
    var similarity = (dotproduct) / (mA * mB)
  }

  return similarity;
}

<p id="cs"></p>
<button onclick="myFunction()">Click</button>

I am trying to get the function to loop through the a array and print out the cosine similarity for each element in the array, however it only prints the first? If I remove the cs variable and calculations, the function prints out all the users. I am not sure why adding the cosine function within the function causes it to only run once?

Any help appreciated, thanks.

replace i = 0 with var i = 0 in your loops

Sergej
– Sergej

2018-07-30 12:52:27 +00:00
Commented Jul 30, 2018 at 12:52 — Sergej
– Sergej, Commented Jul 30, 2018 at 12:52

Pointy · Accepted Answer · 2018-07-30 12:47:51Z

5

You're using the same (global) variable i in both functions. You should declare i as a local variable in each:

var i;

or in the for loops:

for (var i = 0; ...

Because both loops currently use the same i, once the cosinesim() function runs, the loop in the first function will be over too.

If you code in "strict" mode, you get an error from such implicit global uses.

answered Jul 30, 2018 at 12:47

Pointy

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3 Comments

Future Over a year ago

Thanks, did not know it would have created a global variable.

gkgkgkgk Over a year ago

Using a let instead of a var would further improve the scoping of 'i', in case @Future expands his code.

Pointy Over a year ago

@gkgkgkgk yes, true, though old versions of IE and the old Android browser don't support it. That's getting much less important as time goes on of course.

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