number of times a character occurs in a string

[libsfan01]

hi all

how do u get js to work out the number of times a given char occurs in
a given string?

regards

Marc

 

[Randy Webb]

libsfan01 said the following on 8/12/2006 1:34 PM:

hi all

how do u get js to work out the number of times a given char occurs in
a given string?

You count them. Seriously, there is no built in "howManyTimesItOccurs"
type function. You will have to write your own. You also have to decide
whether "M" and "m" are the same or not.

Simple start, there are other ways also that use charAt:

var origString = "My mama told me";
var characterToCount = "m";
var counter = 0;

//if you don't want "M" and "m" to count the same
//remove the .toLowerCase() from the line below

var myArray = origString.toLowerCase().split('');


for (i=0;i<myArray.length;i++)
{
if (myArray == characterToCount)
{
counter++;
}
}
alert('The character ' + characterToCount + ' appears ' +
counter + ' times in the sequence:\n' + origString)

 

[Matt Kruse]

Simple start, there are other ways also that use charAt:
[...]

I don't know if this is generally faster or slower, but I think it's
cleaner:

var str =
"hjahjkahjkahjaguyayafhajagjhajAahkjahkAjahkjahAkjahkjahkjahkjahkjahkja";
String.prototype.count = function(match) {
var res = this.match(new RegExp(match,"g"));
if (res==null) { return 0; }
return res.length;
}
alert(str.count("a"));
alert(str.count("[Aa]"));

 

[Randy Webb]

Matt Kruse said the following on 8/12/2006 3:04 PM:

Simple start, there are other ways also that use charAt:
[...]

I don't know if this is generally faster or slower, but I think it's
cleaner:

It's definitely different

var str =
"hjahjkahjkahjaguyayafhajagjhajAahkjahkAjahkjahAkjahkjahkjahkjahkjahkja";
String.prototype.count = function(match) {
var res = this.match(new RegExp(match,"g"));
if (res==null) { return 0; }
return res.length;
}
alert(str.count("a"));
alert(str.count("[Aa]"));

Is "match" a good name for a parameter? I don't normally use variable
names that are used by JS itself but just curious.

 

[libsfan01]

Thanks again Randy that worked a treat!

regards

marc

libsfan01 said the following on 8/12/2006 1:34 PM:

hi all

how do u get js to work out the number of times a given char occurs in
a given string?

You count them. Seriously, there is no built in "howManyTimesItOccurs"
type function. You will have to write your own. You also have to decide
whether "M" and "m" are the same or not.

Simple start, there are other ways also that use charAt:

var origString = "My mama told me";
var characterToCount = "m";
var counter = 0;

//if you don't want "M" and "m" to count the same
//remove the .toLowerCase() from the line below

var myArray = origString.toLowerCase().split('');


for (i=0;i<myArray.length;i++)
{
if (myArray == characterToCount)
{
counter++;
}
}
alert('The character ' + characterToCount + ' appears ' +
counter + ' times in the sequence:\n' + origString)

 

[Dr John Stockton]

JRS: In article <[email protected]>, dated
Sat, 12 Aug 2006 14:18:48 remote, seen in

libsfan01 said the following on 8/12/2006 1:34 PM:

var origString = "My mama told me";
var characterToCount = "m";

RE = new RegExp("[^" + characterToCount + "]", "gi")
Answer = origString.replace(RE, "").length

Omit the i to count only lower-case.

To count non-overlapping multi-length items, use something similar to
remove all occurrences and then see how much shorter it gets.

var orig = "My mama told me";
var Count = "ma";

RE = new RegExp(Count, "gi")
Answer = (orig.length - orig.replace(RE, "").length) / Count.length


Note that it counts in the string, and not in the literal which
generated it. Consider orig = "\u0033" ; Count = "3" giving 1.

Read the newsgroup FAQ.

 

[Andrew Poulos]

Simple start, there are other ways also that use charAt:
[...]

I don't know if this is generally faster or slower, but I think it's
cleaner:

var str =
"hjahjkahjkahjaguyayafhajagjhajAahkjahkAjahkjahAkjahkjahkjahkjahkjahkja";
String.prototype.count = function(match) {
var res = this.match(new RegExp(match,"g"));
if (res==null) { return 0; }
return res.length;
}
alert(str.count("a"));
alert(str.count("[Aa]"));

What about
var str =
"hjahjkahjkahjaguyayafhajagjhajAahkjahkAjahkjahAkjahkjahkjahkjahkjahkja";

alert( str.length - str.replace(/a/gi,'').length);


Andrew Poulos

 

[Dr John Stockton]

JRS: In article <[email protected]>, dated
Sat, 12 Aug 2006 15:36:46 remote, seen in

Matt Kruse said the following on 8/12/2006 3:04 PM:

ISTM that return +res.length should do for those 2 lines.

}
alert(str.count("a"));
alert(str.count("[Aa]"));

Is "match" a good name for a parameter? I don't normally use variable
names that are used by JS itself but just curious.

It's not a good name, at least in contexts like that, if only because it
raises doubts such as that in the mind of the reader. Synonyms exist.