javascript check if property is defined code example
Example 1: how to check if object is undefined in javascript
if (typeof something === "undefined") {
alert("something is undefined");
}
Example 2: javascript check if boolean is undefined
if (typeof myFlag !== "undefined") {
// comes here whether myFlag is true or false but not defined
}
Example 3: test if property exists javascript
const hero = {
name: 'Batman'
};
hero.hasOwnProperty('name'); // => true
hero.hasOwnProperty('realName'); // => false