JSFiddle - React, Tailwind, and code Playground

JavaScript

var list = "battery.voltage: 13.50\n"
         + "battery.voltage.nominal: 12.0\n"
         + "beeper.status: enabled\n"
         + "device.type: ups\n"
         + "driver.name: blazer_ser\n"
         + "driver.parameter.pollinterval: 2";

// Convert list to an array
var items = list.split(/\n/);

// arr will later contain your key-value pairs.
var arr = {};
for (var i = items.length - 1; i >= 0; i--) {
    var key = items[i].substr(0, items[i].indexOf(':'));
    var value = items[i].substr(items[i].indexOf(':') + 1).trim();
    arr[key] = value;
}

console.log(arr);