I have an array:
var locations = ['Afghanistan','Albania','Algeria','New York'];
and a string:
var string = 'I love Afghanistan New York Afghanistan Andorra Andorra Algeria New York';
I want to count the number of times each keyword in the array appears in the string but can't figure out the best way to do that.
I have an array:
var locations = ['Afghanistan','Albania','Algeria','New York'];
and a string:
var string = 'I love Afghanistan New York Afghanistan Andorra Andorra Algeria New York';
I want to count the number of times each keyword in the array appears in the string but can't figure out the best way to do that.
Share Improve this question asked Sep 9, 2009 at 14:54 StefanHaydenStefanHayden 3,6692 gold badges32 silver badges39 bronze badges4 Answers
Reset to default 5Here is my version:
function countItems(a, s) {
var x, i, output = {};
for (x = 0; x < a.length; x++) {
i = 0;
output[a[x]] = 0;
while ((i = s.indexOf(a[x], i)) > -1) {
output[a[x]]++;
i++
}
}
return output;
}
var result = countItems(locations, string);
// result['Albania'] === 0
Try it out here.
Try something like this. You could modify what you do with count -- store it in another array, display it (which is what this script does), etc.
var locations = ['Afghanistan','Albania','Algeria','New York'];
var str = 'I love Afghanistan New York Afghanistan Andorra Andorra Algeria New York';
for(var i=0; i<locations.length; i++) {
var pattern = new RegExp(locations[i], "g");
var m = str.match(pattern);
if (m != null)
{
var count = m.length; // the count
alert("There are " + count + " occurrences of " + locations[i]);
}
}
<script language="JavaScript">
var locations = ['Afghanistan','Albania','Algeria','New York'];
var string1 = 'I love Afghanistan New York Afghanistan Andorra Andorra Algeria New York';
for (var i=0;i<locations.length;i++) {
nCount = string1.split(locations[i]).length-1;
document.write(locations[i] + ' is found ' + nCount + ' times<br>');
}
</script>
This code only instantiates one RegExp object and uses a reverse while-loop. I'm pretty sure this is as fast as you can go without breaking the laws of physics :)
This is whats happening:
- Construct regular expression string using a reverse while-loop
- New up just one RegExp object, and
match()it on the string - Count the length of the array returned by the
match()function
Here's the implementation:
var countries = ["Afganistan", "America", "Island"];
var sentence = "I love Afganistan, America.. And I love America some more";
function countOccurrences(a, s)
{
var re = "",
l = a.length,
m;
while (l)
{
l--;
re += a[l];
if (l > 0) re += "|";
}
m = s.match(new RegExp(re, "gi")) || [];
return m.length;
}
Note: I am of course expecting the entries in the array to be sanitized for any special characters that will break the regular expression constructed within the function.
var occurrences = function countOccurrences(countries, sentence); // returns 3