how to know if it's a string javascript code example

Example 1: if is a string javascript

function isString(x) {
  return Object.prototype.toString.call(x) === "[object String]"
}

Example 2: check if value is a string javascript

let eventValue = event.target.value;

    if (/^\d+$/.test(eventValue)) {
      eventValue = parseInt(eventValue, 10);
    }

//If value is a string, it converts to integer. 

//Otherwise it remains integer.