check if in object javascript code example

Example 1: check the properties of an object in javascript

for (var name in object) {  
    if (object.hasOwnProperty(name)) { 
        // do something with name                    
    }  
}

// OR

const hero = {
  name: 'Batman'
};

hero.hasOwnProperty('name');     // => true
hero.hasOwnProperty('realName'); // => false

Example 2: test if property exists javascript

const hero = {
  name: 'Batman'
};

hero.hasOwnProperty('name');     // => true
hero.hasOwnProperty('realName'); // => false

Example 3: check if object has method javascript

if(typeof myObj.prop2 === 'function') {
    alert("It's a function");
} else if (typeof myObj.prop2 === 'undefined') {
    alert("It's undefined");
} else {
    alert("It's neither undefined nor a function. It's a " + typeof myObj.prop2);
}

Example 4: javascript check if is object

obj = {
	"data": 123
}
arr = [
	"data", 
	123
]

function obj_or_arr(val) {
	if (typeof val === "object") { // return if is not array or object
		try {
			for(x of val)  // is no errors happens here is an array
				break;
			return "array";
		} catch {
			return "object"; // if there was an error is an object
		}
	} else return false; 
}

console.log(obj_or_arr(obj)) // object
console.log(obj_or_arr(arr)) // array
console.log(obj_or_arr(123)) // false
console.log(obj_or_arr("hello world")) // false
console.log(obj_or_arr(true)) // false
console.log(obj_or_arr(false)) // false

Example 5: javascript check if object

typeof yourVariable === 'object' // true if it's an object or if it's NULL.

// if you want to exclude NULL
typeof yourVariable === 'object' && yourVariable !== null

Example 6: checking a condition in object javascript

{  id: 'some-id',  ...(true && { optionalField: 'something'})}