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TypeScript - check if object has property or function
0 points
In TypeScript it is possible to check if object has property or method (function) in following ways.
This approach checks only entries that are directly inside object.
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interface Student {2
name: string;3
age: number;4
}5
6
const student: Student = {7
name: 'John',8
age: 25,9
};10
11
console.log(student.hasOwnProperty('name')); // true12
console.log(student.hasOwnProperty('age')); // true13
console.log(student.hasOwnProperty('country')); // falseOutput:
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true2
true3
falseThis approach checks elements that are inside prototype chain.
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interface Student {2
name: string;3
age: number;4
}5
6
const student: Student = {7
name: 'John',8
age: 25,9
};10
11
console.log('name' in student); // true12
console.log('age' in student); // true13
console.log('country' in student); // falseOutput:
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true2
true3
falseNote: be careful during using this approach because of inherited properties and methods e.g. true value for 'toString' in student expression.
