JSFiddle - React, Tailwind, and code Playground

JavaScript

var data = {
    tickets: [{
        tag: 'assistance'
    }, {
        tag: 'bug'
    }, {
        tag: 'evolution'
    }, {
        tag: 'assistance'
    }, {
        tag: 'bug'
    }, {
        tag: 'assistance'
    }, {
        tag: 'maintenance'
    }]
}
var occurrences = {};
for (i = 0; i < data.tickets.length; i++) {
    // your code here...

    var tag = data.tickets[i].tag;
    if (occurrences.hasOwnProperty(tag)) {
        occurrences[tag]++;
    } else {
        occurrences[tag] = 1;
    }
}

console.log(occurrences);