Count counts per string from array of keywords in javascript
I have an array:
var locations = ['Afghanistan','Albania','Algeria','New York'];
and the line:
var string = 'I love Afghanistan New York Afghanistan Andorra Andorra Algeria New York';
I want to count the number of times each keyword in an array appears in a row, but cannot find a better way to do it.
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Here's 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 here .
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Try something like this. You can change what you are doing from 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]);
}
}
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<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>
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This code only instantiates one object RegExp
and uses the reverse while-loop. I'm sure this is as fast as you can go without breaking the laws of physics :)
This is what happens:
- Construct regex string with reverse while-loop
- Create only one RegExp object and
match()
it's on a line - Count the length of the array returned by the function
match()
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 would of course expect the entries in the array to be sanitized for any special characters that would ruin the regex built inside the function.
var occurrences = function countOccurrences(countries, sentence); // returns 3
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