JSFiddle - React, Tailwind, and code Playground

HTML

<div id="nums"></div>

JavaScript

nums = [1, 2, 3, 'привет'];

Array.prototype.sum = function() {
    s = 0;
    l = this.length;
    for (i = 0; i < l; i++) {
        if (!isNaN(parseFloat(this[i])) && isFinite(this[i])) {
            s += this[i];
        } 
    }
    return s;
}

document.getElementById("nums").innerHTML = nums.sum();