Reputation: 11
I'm trying to write a Javascript function that counts the vowels in a string by calling another function inside that function, but when I test it in the console it returns 0.
Here is my first function that works fine and recognizes if a string is a vowel:
function isVowel(ch){
var pattern = /[aeiouAEIOU]/
return pattern.test(ch);
};
For the second function none of my ideas have worked. Here are a few examples of what I have tried so far:
This one returns me a 0:
function countVowels(str){
var count = 0;
for(var i; i <= str.length; ++i){
if(isVowel(i)){
++count;
}
}
return count;
};
I also tried the above, but removing the .length after str in the for() area.
Another example, but this one gives me an error:
function countVowels(str){
var count = 0
var pattern = /[aeiouAEIOU]/
for(var i = 1; i <= str.length(pattern); ++i){
if(isVowel(i)){
++count;
}
}
return count;
};
I've tried various other functions as well, but for the sake of keeping this post relatively short I won't continue to post them. I'm quite new to Javascript and I'm not sure what I'm doing wrong. Any help would be greatly appreciated!
Upvotes: 0
Views: 1078
Reputation: 7315
Although Robiseb answer is the way to go, I want to let you know why you code is not working (I'm referring your first attempt). Basically you made two mistakes in the loop:
As CBroe stated, you are passing i
to your isVowel
function. i
is a integer representing the index of the loop, not the actual character inside the string. To get the character you can do str.substr(i, 1)
, what means "give me one character from the position i
inside the string".
You are not giving a initial value to the i
variable. When you create a variable, it is undefined, so you can not increment it.
alert(countVowels("hello"));
function countVowels(str) {
var count = 0;
for (var i = 0; i <= str.length; ++i) {
if (isVowel(str.substr(i, 1))) {
count++;
}
}
return count;
};
function isVowel(ch) {
var pattern = /[aeiouAEIOU]/
return pattern.test(ch);
};
UPDATE: You will see that other answers use other methods to select the character inside the string from the index. You actually have a bunch of different options. Just for reference:
str.slice(i,i+1);
str.substring(i,i+1);
str.substr(i,1));
str.charAt(i);
str[i];
Upvotes: 1
Reputation: 26136
Obviously you should do it this way:
function isVowel(c){
var lc = c.toLowerCase();
if(lc === 'y'){
return (Math.floor(Math.random() * 2) == 0);
}
return ['a','e','i','o','u'].indexOf(lc) > -1;
}
function countVowels(s){
var i = 0;
s.split('').each(function(c){
if(isVowel(c)){
i++;
}
});
return i;
}
console.log(countVowels("the quick brown fox jumps over the lazy dog"));
Which, although less efficient and less useful than other answers, at least has the entertaining property of returning a different count 50% of the time, because sometimes Y.
Upvotes: 0
Reputation: 2380
You forgot to assign the value 0 to i variable
And parameter for isVowel is the character, not the index of string
Here information about the JS language: https://stackoverflow.com/tags/javascript/info
function isVowel(ch){
var pattern = /[aeiouAEIOU]/
return pattern.test(ch);
}
function countVowels(str){
var count = 0;
// you forgot to assign the value to i variable
for(var i = 0; i < str.length; i++){
// isVowel(str[i]), not isVowel(i)
if(isVowel(str[i])){
count++;
}
}
return count;
}
console.log(countVowels('forgot'))
Upvotes: 0
Reputation: 1606
Try using .match()
with the g
attribute on your String.
g
: global
i
: case insensitive
function countVowels(ch){
return ch.match(/[aeiouy]/gi).length;
}
var str = "My string";
alert(countVowels(str)); // 2
Upvotes: 1
Reputation: 782785
i
is the index, not the character. It should be:
if (isVowel(str[i])) {
count++;
}
Also, str.length(pattern)
is wrong. length
is a property, not a function, so it should just be str.length
.
Upvotes: 0