JSFiddle - React, Tailwind, and code Playground

JavaScript

function format(input) {
    return input.toLocaleString("en", { 
        useGrouping: true, 
        maximumFractionDigits: 8 
    });
}

var numbers = [121, 14231.439400000, 1.123456789, -9012.4430001];
for(var i = 0; i < numbers.length; i++) {
    $("<p>").text(format(numbers[i])).appendTo("body");
}