javascript - Using for loop to find specific characters in string - Stack Overflow

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I am attempting the bean counting example in the functions chapter of the book Eloquent Javascript. My function is returning a blank.

Without giving me the full answer (I'm working through this example to learn), can someone tell me why my code is not printing any text?"

var string = "donkey puke on me boot thar be thar be!";

for (var i = 0; i <= string.length; i++);

function getB(){
  if (string.charAt(i) == "b")
    return i;
  else return "";
}

console.log(getB());

I am attempting the bean counting example in the functions chapter of the book Eloquent Javascript. My function is returning a blank.

Without giving me the full answer (I'm working through this example to learn), can someone tell me why my code is not printing any text?"

var string = "donkey puke on me boot thar be thar be!";

for (var i = 0; i <= string.length; i++);

function getB(){
  if (string.charAt(i) == "b")
    return i;
  else return "";
}

console.log(getB());

• javascript

Share Improve this question Follow edited Feb 23, 2015 at 13:11 Bergi 666k161161 gold badges1k1k silver badges1.5k1.5k bronze badges asked Feb 23, 2015 at 12:43 AndrewAndrew 74722 gold badges88 silver badges2424 bronze badges 5

• 1 Why does your loop have an empty body? Where would getB get its i variable from? – Bergi Commented Feb 23, 2015 at 12:48
• 2 ♫ I am a lonely programmer, i ain't got no body. – Andy Commented Feb 23, 2015 at 12:49
• Lose the ; after the for(), make the next line console.log(getB(i)) change to function getB(i){... – Alex K. Commented Feb 23, 2015 at 12:49
• 1 if you want to search the location of your string, you can use string.indexOf("b"); or write your own function which traverses trough the whole string. (use the function as the body for your loop and use just the first condition) – Raphael Müller Commented Feb 23, 2015 at 12:51
• 1 @RaphaelMüller: Actually that's not the task – Bergi Commented Feb 23, 2015 at 13:11

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6 Answers 6

Sorted by: Reset to default 2

There is something wrong about how you're trying to implement this feature. First of all I think it's better if you have a function that accepts the string and the char as parameters in order to call it whenever you want.

Example of calling :

getChar('this is my custom string', 'c')  -> it should search character `c` in `this is my custom string`

getChar('this is another custom string', 'b')  -> it should search character `b` in `this is another custom string`

Example of implementation :

var getChar = function(string, char){
  for(var i=0;i<string.length;i++)
  {
    if(string.charAt(i)==char) console.log(i);
  }
}

Now, try to make it not case-sensitive and instead of console.log the output try to return a sorted array with character positions

Use This,

var string = "donkey puke on me boot thar be thar be!";

for (var i = 0; i <= string.length; i++) {
  if (string.charAt(i) == "b") {
    console.log(i);
  }
}

if you want to print every position your value is at, you can program something like this:

var string = "donkey puke on me boot thar be thar be!";

for (var i = 0; i <= string.length; i++)
{
   getChar(i, "b");
}

function getChar(i, input)
{
    if (string.charAt(i) == input)
        console.log(i);
}

another example: collect all b positions:

var string = "donkey puke on me boot thar be thar be!";

function getB(string){
    var placesOfB = [];
    for (var i = 0; i < string.length; i++) {
        if (string.charAt(i) == "b") {
            placesOfB.push(i);
        }
    }
    return placesOfB;
}

console.log(getB(string));

tip: your for has no body (putting ; after it just loops without doing anything)... and it does not make sense to define a function inside that for.

Without giving you the full answer, I'll just give you pointers: 1. Your for loop is not plete - it doesn't do anything. 2. Your getB() function needs to accept string parameter in order to perform some action on it. 3. The if..else statement doesn't have opening and closing brackets {}

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