JavaScript, brackets on for loop causing errors?

Question

I have a function that takes an input of a string and a single char that will count how many times that char appears in that string.

function count(str, letter) {
  var num = 0;
  for (var i = 0; i < str.length; i++)
    if (str.charAt(i) == letter)
      num += 1;
  return num;

}

console.log(count("BBC", "B"));
//output 2

It works fine like this, but this took me some time to figure out. Its second hand nature for me to always put brackets on a for loop but when i do that, the function doesn't work as i anticipated it would, like so:

function count(str, letter) {
  var num = 0;
  for (var i = 0; i < str.length; i++) {
    if (str.charAt(i) == letter)
      num += 1;
    return num;
  }
}

console.log(count("BBC", "B"));
//outputs 1

Why are the brackets causing it to act this way?

Nina Scholz · Accepted Answer · 2017-06-24 07:16:59Z

1

Why are the brackets causing it to act this way?

Because you have the return statement inside of the for loop block. At the end of the block, the function returns.

function count(str, letter) {
    var num = 0;
    for (var i = 0; i < str.length; i++) {  // block start
        if (str.charAt(i) == letter)
            num += 1;
        return num;                                        // exit function in first loop
    }                                       // block end
}

answered Jun 24, 2017 at 7:16

Nina Scholz

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Comments

Wheeler · Accepted Answer · 2017-06-24 07:20:27Z

0

It's not the braces (brackets are []), it's the placement of the return statement. The return statement is in the first iteration of the loop (i = 0). If you add an extra set of braces (as seen below), it becomes more obvious.

function count(str, letter) {
    var num = 0;
    for (var i = 0; i < str.length; i++) {
        if (str.charAt(i) == letter) {
            num += 1;
        }
        return num; // <-- This return exits the function
    }
}

console.log(count("BBC", "B"));
//outputs 1

answered Jun 24, 2017 at 7:20

Wheeler

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Comments

Sunjith · Accepted Answer · 2017-06-24 07:23:44Z

0

In the First one return statement was outside for loop, but in the second one return statement is inside the for loop. That made the difference. Try the below code.

    function count(str, letter) {
      var num = 0;
      for (var i = 0; i < str.length; i++) {
        if (str.charAt(i) == letter)
          num += 1;
        }
        return num;
    }

console.log(count("BBC", "B"));

answered Jun 24, 2017 at 7:23

Sunjith

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Comments

Ilario Pierbattista · Accepted Answer · 2017-06-25 11:32:04Z

0

your loop gets terminated after first iteration. So if you try to get the occurrence of "B" in "XBBBB...B" it will return 0. Try to debug your code and place brackets at right position. Learn to debug your js code using browser.

edited Jun 25, 2017 at 11:32

Ilario Pierbattista

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answered Jun 24, 2017 at 7:30

Rohan Mehta

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