How to release the reference to HTML to the different text

[zymir]

The formulas for correct entry are checked. Under the formula, we need to indicate a ^ position where there is an incorrect entry.

(a+b) - (a-b)
(a+b - (a-b

^      ^

[Avante]

Just check the number of open and closed brackets. If the numbers don't match, there's a mistake. But the function only finds one mistake.

Take an error @Sergiks

$('input').on('change', function() {
  var value = this.value;
  var opened = 0;
  var last = 0;
for(var i=0, sp=value.split(""); i < sp.length; i++) {

if(sp[i] == "(") {

last = i;

opened++;

}
if(sp[i] == ")"){
  last = i;
  opened--;
}

if(opened &lt; 0) {
   show_error(last);
   break;
}

}
if(opened != 0) {

show_error(last);

}
});
function show_error(sym_no) {

alert(sym_no);

}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<input>