Javascript: search string in array then count occurrences

Question

I am using indexOf to search for a string in an array, how can I continue to count the number of occurences? I tried the latter but it isn't working.

var feed= new Array();
var feed= ["testABC", "test", "testABC"];

if (feed.indexOf("testABC") != -1) {
    for (var i=0; i < feed.indexOf("testABC").length; i++ ) {
        logInfo("found"+feed++);
    }
}

You might want to take a look at the [Array iteration methods](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array#Iteration_methods). These are nearly always more appropriate than a for-loop. — 1983, Jun 07 '16 at 19:52
Possible duplicate of [Count instances of string in an array](http://stackoverflow.com/questions/9996727/count-instances-of-string-in-an-array) — 1983, Jun 07 '16 at 20:35

score 5 · Accepted Answer · answered Jun 07 '16 at 18:42

You can set a count variable and iterate over the elements of feed. Then check if the element has indexOf unequal -1 (means found) and count the occurence.

var feed = ["testABC", "test", "testABC"],
    count = 0,
    i;

for (i = 0; i < feed.length; i++) {
    if (feed[i].indexOf("testABC") !== -1) {
        count++;
    }
}

console.log(count);

Sergey Khalitov · Answer 2 · 2016-06-07T18:52:29.627

4

Try to use Array.prototype.forEach function:

var feed  = ['foo','testABC','bar','testABC','testABC'];
var count = 0;
feed.forEach(function(value){
    if(value=='testABC') count++;
});
console.log(count); //3

Or Array.prototype.filter function:

var feed  = ['foo','testABC','bar','testABC','testABC'];
var count = feed.filter( function(value) { return value=='testABC' } ).length;
console.log(count); //3

edited Jun 07 '16 at 18:52

answered Jun 07 '16 at 18:42

Sergey Khalitov

959
7
16

score 2 · Answer 3 · answered Jun 07 '16 at 18:46

2

var numOfString = 0;
var feed= new Array()
var feed= ["testABC", "test", "testABC"]

for(var i=0;i<feed.length;i++){
    if(feed[i] === "testABC")
       numOfString++;
}
console.log(numOfString);

answered Jun 07 '16 at 18:46

Tanvi B

1,479
9
13

Nika · Answer 4 · 2016-06-07T20:11:29.960

2

try:

var feed = ["testABC", "test", "testABC"],
count = feed.filter(function(v) { return v.indexOf('test') > -1; }).length;

EDIT: removed duplicate feed = feed. also, I had startsWith instead of indexOf. It should work now.

edited Jun 07 '16 at 20:11

answered Jun 07 '16 at 18:47

Nika

1,774
3
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You've written `var feed =` twice. But even corrected it does not work. – Oleg Mikhailov Jun 07 '16 at 19:54

score 2 · Answer 5 · answered Jun 07 '16 at 18:48

Here's a simple and straight forward solution. You may want to make it a function in the case that you want to reuse your code.

var feed= new Array()
var feed= ["testABC", "test", "testABC"]
var count = 0

// ensure that our array contains the key you want prior to scanning it
if(feed.findIndex("testABC") >= 0) {
    for (var i=0; i < feed.length; i++ ) { 
    if(feed[i] === "testABC") count++
  }
}

alert(count)

score 2 · Answer 6 · answered Jun 07 '16 at 18:51

In addition to all the ways the other stated, if you are using ES6 you can use the 'for of' loop to iterate all the array's values:

var numOfString = 0;
var feed = ["testABC", "test", "testABC"];
for(let currentString of feed) {
  if(currentString.indexOf('testABC') !== -1) {
    numOfString += 1;
  }
}
console.log(numOfString);

score 2 · Answer 7 · answered Jun 07 '16 at 19:09

2

It can be achieved with one line of code using ES6 arrow function expression:

var feed = ["testABC", "test", "testABC"], count = 0;

feed.forEach((v) => v === "testABC" && count++);

console.log(count);  // 2

answered Jun 07 '16 at 19:09

RomanPerekhrest

75,918
4
51
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@OlegMikhailov, I don't think so. That is not too complicated case to talk about readability. Too simple – RomanPerekhrest Jun 07 '16 at 19:29
Yeah, but who knows what this function becomes in future... It is always a good time to talk about readability). Programs are written for humans then. – Oleg Mikhailov Jun 07 '16 at 19:38
@OlegMikhailov, " but who knows" - nobody knows. When someone will ask for the extended and complex case - I'll write new solution. But for now, "one-line" solution will be also good – RomanPerekhrest Jun 07 '16 at 19:50

score 1 · Answer 8 · edited May 23 '17 at 10:34

1

If feed = ["testABC testABC"] counts as two occurences of "testABC", then I suggest the following code:

var feed = ["testABC", "test", "testABC"];

var count = (feed.join('').match(/testABC/g) || []).length;

console.log(count)

See also How to count string occurrence in string?

Arbitrary search strings would need escaping for special regex characters.

edited May 23 '17 at 10:34

Community

1
1

answered Jun 07 '16 at 19:20

le_m

17,771
9
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score 0 · Answer 9 · answered May 16 '18 at 13:22

0

You can also use regular expressions and the String.prototype.match()

Code:

const feed = ["testABC", "test", "testABC"];
const count = feed.toString().match(/testABC/g).length;

console.log(count)

answered May 16 '18 at 13:22

Yosvel Quintero Arguelles

17,270
4
37
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score 0 · Answer 10 · answered May 17 '22 at 20:01

0

Or you can simply use reduce() method:

    const feed = ["testABC", "test", "testABC", 'testABC'];

    const count = feed.reduce((acc, val) => (acc[val] = acc[val] + 1 || 1, acc), {})['testABC']

    console.log(count)

answered May 17 '22 at 20:01

codecumber

72
1
8

Javascript: search string in array then count occurrences

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