CODEWITHSUNDEEP
javascriptarrayscount
Bobdinator
Bobdinator

Reputation: 137

JavaScript: Number of given string in array

Not sure how to explain this in words, but is there any function in javascript that, when given a string , will return the number of times it occurs in an array?

For example:

var arr = ["a","b","c","d","c","c","b"];
var repeats = arr.count("c");

With repeats then being equal to 3 as "c" occurs 3 times. I tried to look this up but I wasn't sure on how to word it so I didn't get anything useful.

Upvotes: 1

Views: 56

Answers (4)

vol7ron
vol7ron

Reputation: 42179

Exact Word Match Example

var search_word = 'me';
var arr = ['help','me','please'];
arr.filter(function(el){return el === search_word}).length;

The filter function will return the element if the result of the function is true. The function is called on each element of the array. In this case, we are comparing the array element to our search word. If they are equal (true) the element is returned. We end up with an array of all the matches. Using .length simply gives us the number of items in the resulting array; effectively, a count.

Partial Match Example

If you were to want something a little more robust, for instance count the number of words that contain the letter l, then you could tokenize the string and scan the index, or use some regex which is a little more costly, but also more robust:

var search_word = 'l';
var arr = ['help','me','please'];
arr.filter( function(el){ return ( el.match(search_word) || [] ).length }).length;

Note that match also returns an array of matching elements, but an unsuccessful match returns undefined and not an empty array, which would be preferred. We need an array to use .length (the inside one), otherwise it would result in an error, so we add in the || [] to satisfy the case when no matches are found.

Upvotes: 0

chaslewis
chaslewis

Reputation: 306

arr.filter(function(v){return v=='c';}).length

Upvotes: 0

epascarello
epascarello

Reputation: 207557

You can use array.filter()

var arr = ["a","b","c","d","c","c","b"];
var repeats = arr.filter(function(value) { return value==="c"; } ).length;
console.log(repeats)

Upvotes: 1

TheDude
TheDude

Reputation: 3952

You can create your own function or add it to the prototype of Array: 

Array.prototype.count = function (val){ 
      var result = 0;
      for(var i = 0; i < this.length; i++){
        if(this[i] === val) result++;
      }

      return result;
}

Then you can do ['a','b', 'a'].count('a') // returns 2

Upvotes: 3

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