Get number of occurrences of a character in JavaScript [duplicate]

Answer 1

Count number of matches of a regex in Javascript

you need the /g global flag

Edit: I didn't need the 'ticks' below.

var count = string.match(/,/g).length; 

Answer 2

If you need to check the occurances of a simple pattern as "," then better don't use regular expressions.

Try:

var matchesCount = string.split(",").length - 1;

Answer 3

This gives null because '/[,]/i' is not a regex. As explained at the MDN, if a non-regex is passed to string.match, then it will be converted to a regex using new Regex(obj).

What you want is to pass the actual regex object, /[,]/i (or simply /,/i). "1,2,3".match(/,/i) will work as you expect in terms of matching.

However, as Cybernate pointed out, a regex is overkill for this kind of problem. A better solution is to split the string:

var str = "1,2,3,4,5";
var len = str.split(",").length - 1;

Answer 4

Remove the quotes and add the g flag:

var str = "This, is, another, word, followed, by, some, more";
var matches = str.match(/,/g);
alert(matches.length);    // 7

jsfiddle here: http://jsfiddle.net/jfriend00/hG2NE/

Answer 5

This gist claimed that regexp was the most efficient technique.

Edit: However the performance benchmark provided by Job in the comments suggest that the split technique is now faster. So I would recommend that nowadays.

But anyway, if you do go with the regexp approach, you should be aware that if there are no matches, then String::match() returns null, and not an empty array as you might expect:

> 'foo'.match(/o/g)
[ 'o', 'o' ]

> 'foo'.match(/o/g).length
2

> 'foo'.match(/x/g)
null

> 'foo'.match(/x/g).length
TypeError: Cannot read property 'length' of null

One simple way to deal with this is to substitute an empty array if the result is null:

var count = (string.match(/,/g) || []).length;

Or this avoids creating the empty array, but requires two lines of code:

var match = string.match(/,/g);
var count = match ? match.length : 0;

Answer 6

function get_occurrence(varS,string){//Find All Occurrences
    c=(string.split(varS).length - 1);
    return c;
}
string="Hi, 1,2,3";
console.log(get_occurrence(",",string));

Use get_occurrence(varS,string) to find occurrence of both characters and string in a String.