JSFiddle - React, Tailwind, and code Playground

JavaScript

function arrIndex(fnd,arr){
    for(var len=arr.length,i=0;i<len;i++){
        if(i in arr&&arr[i]===fnd){
            return i;
        }
    }
    return -1;
}

function scrapeNumbers(str){
    var arr=str.replace(/,+/g,",").replace(/^,/,"").replace(/,$/,"").split(",");
    for(var i=0,len=arr.length,rtn=[];i<len;i++){
        if(i in arr&&arrIndex(arr[i],rtn)==-1){
            rtn.push(arr[i]);
        }
    }
    return rtn.join(",");
}

var str=",,34,23,4,5,634,23,12,5,4,3,1234,23,54,,,,,,,123,43,2,3,4,5,3424,,,,,,,,123,,,1234,,,,,,,45,,,56,,";

alert(scrapeNumbers(str));