How to count Matching values in Array of Javascript

Question

please tell me any good algorithm/code to get list of unique values from array and count of its occurrence in array. (i am using javascript).

Answer 1

Use an object as an associative array:

var histo = {}, val;
for (var i=0; i < arr.length; ++i) {
    val = arr[i];
    if (histo[val]) {
        ++histo[val];
    } else {
        histo[val] = 1;
    }
}

This should be at worst O(n*log(n)), depending on the timing for accessing object properties. If you want just the strings, loop over the object's properties:

for (val in histo) {...}