JSFiddle - React, Tailwind, and code Playground

HTML

<button id="btnm0">-</button><input type="text" id="txt0" /><button id="btnp0">+</button><br/>
<button id="btnm1">-</button><input type="text" id="txt1" /><button id="btnp1">+</button><br/>
<button id="btnm2">-</button><input type="text" id="txt2" /><button id="btnp2">+</button><br/>
<button id="btnm3">-</button><input type="text" id="txt3" /><button id="btnp3">+</button><br/>
<button id="btnm4">-</button><input type="text" id="txt4" /><button id="btnp4">+</button><br/>
<button id="btnm5">-</button><input type="text" id="txt5" /><button id="btnp5">+</button><br/>

JavaScript

window.onload=function(){
    var sumar=function(cantidad,txt){
        txt.value=(!isNaN(txt.value) && txt.value!="")?parseInt(txt.value)+cantidad:0;
    }
    var SUMADORES=[];
    for (var i=0;i<6;i++)
    {
        var obj= {
            btnResta: document.getElementById("btnm"+i),
            btnSuma: document.getElementById("btnp"+i),
            txt: document.getElementById("txt"+i)
        };
        (function (aux) { aux.btnResta.onclick=function(){ sumar(-1,aux.txt); }; })(obj);
        (function (aux) { aux.btnSuma.onclick=function(){ sumar(1,aux.txt); }; })(obj);
        SUMADORES.push(obj);
    }
}