how to detect javascript in a string code example

Example 1: javascript string contains

var string = "foo",
var substring = "oo";

console.log(string.includes(substring));

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.