Question

How to check if a property in object is defined or undefined with TypeScript

Answer 1

const user = {
   languages: {
    	a: 'c++',
        b: 'typescript'
  },
  id: 83829,
  name: undefined
};
 
if (typeof user.languages.a === 'undefined') {
    console.log('user.language.a: undefined');
} else {
	console.log('user.language.a: defined');
}
 
if (typeof user.name === 'undefined') {
    console.log('user.name: undefined');
}

if (typeof user.age === 'undefined') {
    console.log('user.age: undefined');
}
 
if (typeof user.id === 'undefined') {
    console.log('user.id: undefined');
}
else {
    console.log('user.id: defined');
}
 
 
 
 
 
/*
run:
           
"user.language.a: defined" 
"user.name: undefined" 
"user.age: undefined" 
"user.id: defined" 
         
*/

 

70+ SQL courses for beginners and professionals