javascript - How to check if variable is of type function Number() or function String() js -

in javascript. how can test if variable equal function number() or function string().

i reading react prop schema definition type set property. have this.props.fieldtype function number() or function string().

i have tried:

 if(this.props.fieldtype instanceof number) 

and

if(object.getprototypeof(this.props.fieldtype) === number.prototype) 

according instanceof description not work. not sure why.

trying check if property has value of function number() of function string()

if literally mean the functions number or string, use == (or ===):

if (this.props.fieldtype === number) { 

if mean "is number" or "is string", use typeof, not instanceof:

if (typeof this.props.fieldtype === "number") { 

if mean "is object created via new number" (which unusual) instanceof want:

if (this.props.fieldtype instanceof number) { 

examples of three:

var props = {    numberfunction: number,    number: 42,    numberobject: new number(42)  };  console.log(props.numberfunction === number);  console.log(typeof props.number === "number");  console.log(props.numberobject instanceof number);

---

you mentioned instanceof in relation doing getprototypeof , equality comparison. it's imporant understand different things.

instanceof checks see if object (the left-hand operand) has current prototype property of function (the right-hand operand) anywhere in prototype chain. may not object's immediate prototype; may further down. example:

function thing() {  }  var t = new thing();  // following true, object.prototype in t's prototype chain  console.log(t instanceof object);  // following false, t's prototype isn't object.prototype;  // object.prototype further down t's prototype chain  console.log(object.getprototypeof(t) === object.prototype);