JSFiddle - React, Tailwind, and code Playground

JavaScript

data = [
    {
        "Week": "1145",
        "Sev_Logged": "3_major",
        "From": "polo"
    },
    {
        "Week": "1145",
        "Sev_Logged": "4_minor",
        "From": "IN1"
    },
    {
        "Week": "1145",
        "Sev_Logged": "4_minor",
        "From": "IN1"
    },
    {
        "Week": "1145",
        "Sev_Logged": "4_minor",
        "From": "IN1"
    },
    {
        "Week": "1145",
        "Sev_Logged": "4_minor",
        "From": "IN1"
    },
    {
        "Week": "1145",
        "Sev_Logged": "4_minor",
        "From": "IN2"
    },
    {
        "Week": "1145",
        "Sev_Logged": "3_major",
        "From": "IN2"
    }
];

function countBy(data, param) {
    var count = {};
    Ext.each(data, function(item){
        var type = item[param];
        if (Ext.isDefined(count[type]))  {
            count[type]++;
        } else {
            count[type] = 1;
        }  
    });
    return count;
}

console.log(countBy(data, "From"));