Automatic grouping of Iban-Numbers, supporting Backspace- and Del-Keys.

iban_grouping.js

// <input type="text" id="iban">

document.getElementById('iban').addEventListener('input', function (e) {
	var target = e.target, position = target.selectionEnd, length = target.value.length; 
  target.value = target.value.replace(/[^\dA-Za-z]/g, '').replace(/(.{4})/g, '$1 ').trim();
	if(e.inputType === 'deleteContentForward') {
		target.selectionEnd = position += ((target.value.charAt(position) === ' ') ? 1 : 0);
	} else {
		target.selectionEnd = position += ((target.value.charAt(position - 1) === ' ' && target.value.charAt(length - 1) === ' ' && length !== target.value.length) ? 1 : 0);
		if(target.selectionEnd % 5 === 0) {
			if( target.value.length % 5 !== 1 ) {
				target.selectionEnd++;
				target.selectionStart = target.selectionEnd;
			}
		}
	}
});