JS: Reflect.has

(new in ECMAScript 2015)

Reflect.has(obj, key)

Return true if obj has (own or inherited) property key key (string key or Symbol key). Else false.

If obj is not Object Type , it's TypeError.

🟢 TIP: This function is similar to the syntax in (operator), but in a function form. Function form lets you manipulate expressions at run-time.

const xdad = { pp: 3 };
const xson = {};
Reflect.setPrototypeOf(xson, xdad);

// check inherited property
console.assert(Reflect.has(xson, "pp") === true);

// check own property
console.assert(Reflect.has(xdad, "pp") === true);

// Reflect.has works with symbol key

const jj = {};

// add a symbol key
const xsym = Symbol();
jj[xsym] = 4;

console.assert(Reflect.has(jj, xsym));

// if argument is not a object, it's TypeError

try {
 Reflect.has(3, "x");
} catch (xerror) {
 console.log(xerror);
}

// TypeError: Reflect.has called on non-object