How to check if a JavaScript object property is undefined
In a JavaScript program, the correct way to check if an object property is undefined is to use the `typeof` operator. See how you can use it with this simple explanation
In a JavaScript program, the correct way to check if an object property is undefined is to use the typeof
operator.
typeof
returns a string that tells the type of the operand. It is used without parentheses, passing it any value you want to check:
const list = []
const count = 2
typeof list //"object"
typeof count //"number"
typeof "test" //"string"
typeof color //"undefined"
If the value is not defined, typeof
returns the ‘undefined’ string.
Now suppose you have a car
object, with just one property:
const car = {
model: 'Fiesta'
}
This is how you check if the color
property is defined on this object:
if (typeof car.color === 'undefined') {
// color is undefined
}
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