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Along with getter methods, we can also create setter methods which reassign values of existing properties within an object. Let’s see an example of a setter method:
const person = {
_age: 37,
set age(newAge){
if (typeof newAge === 'number'){
this._age = newAge;
} else {
console.log('You must assign a number to age');
}
}
};
Notice that in the example above:
We can perform a check for what value is being assigned to this._age.
When we use the setter method, only values that are numbers will reassign this._age
There are different outputs depending on what values are used to reassign this._age.
Then to use the setter method:
person.age = 40;
console.log(person._age); // Logs: 40
person.age = '40'; // Logs: You must assign a number to age
Setter methods like age do not need to be called with a set of parentheses. Syntactically, it looks like we’re reassigning the value of a property.
Like getter methods, there are similar advantages to using setter methods that include checking input, performing actions on properties, and displaying a clear intention for how the object is supposed to be used. Nonetheless, even with a setter method, it is still possible to directly reassign properties. For example, in the example above, we can still set ._age directly:
person._age = 'forty-five'
console.log(person._age); // Prints forty-five
Instructions
Instructions
1.Currently, in robot there is a getter method for numOfSensors but no setter method! What if we need to add or remove some sensors? Let’s fix that problem.
Add a setter method named numOfSensors using the set keyword. Provide a parameter of num. Leave the function body empty for now.
2.There are a couple of things we should do in the setter method:
Add a check to see if num is a number using the typeof operator.
num should also be greater than or equal to 0.
If both conditions are met, reassign this._numOfSensors to num.
3.Now add an else that logs 'Pass in a number that is greater than or equal to 0' to the console.
4.Use the numOfSensors setter method on robot to assign _numOfSensors to 100.
5.To check that the setter method worked, console.log() robot.numOfSensors.
app.js
app.js
const robot = {
_model: '1E78V2',
_energyLevel: 100,
_numOfSensors: 15,
get numOfSensors(){
if(typeof this._numOfSensors === 'number'){
return this._numOfSensors;
} else {
return 'Sensors are currently down.'
}
},
};
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