JAVASCRIPT

check if value string js

var value = "test string"
console.log(typeof value === "string")

javascript if value is a string function

function isString(value) { 
	if (typeof value === "string") { 
		return true; 
	} 
	return false; 
}

if variable is string javascript

var booleanValue = true; 
var numericalValue = 354;
var stringValue = "This is a String";
var stringObject = new String( "This is a String Object" );
alert(typeof booleanValue) // displays "boolean"
alert(typeof numericalValue) // displays "number"
alert(typeof stringValue) // displays "string"
alert(typeof stringObject) // displays "object"

if is a string javascript

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

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.

check if string javascript

it is better to check with isFinite() rather than typeof or isNAN() 
check this:
var name="somename",trickyName="123", invalidName="123abc";
typeof name == typeof trickyName == typeof invalidName == "string"
isNAN(name)==true
isNAN(trickyName)==false
isNAN(invalidName)==true
where:
isFinite(name) == false
isFinite(trickyName)== true
isFinite(invalidName)== true  
so we can do:
if(!isFinite(/*any string*/))
  console.log("it is string type for sure")
notice that:
	isFinite("asd123")==false
	isNAN("asd123")==true