JSFiddle - React, Tailwind, and code Playground

HTML

<input id="test" type="text" name="iban" onkeyup="if(this.value.length > 34){this.value=this.value.substr(0, 34);}" />

JavaScript

//Keys pressed 0 times
var downed = 0; 
$('#test').keydown(function (g) {
    if(g.code.match("^Digit")){
    	downed++;
      console.log(g)
    }
    
    if(downed == 1){
        var reformat = this.value.replace(/(\d{4}\s*)/g, function(match){
            //Strip spaces
            if(match.match(/\s/)){return match;}
            return match + " ";
    });
    console.log(reformat);
    this.value = reformat; 
    //Start recount
        downed = 0;
    }
});