I need your help, my friends.
There is a task:
Implement Calc class with sub / add / result methods.
In the constructor, we can pass the initial immutable value (by default 0), then add and subtract from it using the add and sub methods.
The add / sub call can be chained (fluent interface), the methods return a new class object.
By calling result (), we get the result of the calculations.
For example:
const calc = new Calc();
calc.result(); // 0
calc.add(5).result(); // 0 + 5 = 5
calc.add(3).sub(10).result(); // 0 + 3 - 10 = -7
const ten = calc.add(10);
ten.sub(5).result(); // 10 - 5 = 5
ten.result(); // 10
This is a class
class Calc {
}
My try:
class Calc {
constructor (num = 0) {
this.num = num;
}
add (a) {
this.num += a
return this
}
sub (a) {
this.num -= a
return this
}
result () {
return this.num
}
}
The test shows it:
FAIL test.js
calc
✓ must return an instance of the Calc class in sub methods (5ms)
✓ must implement fluent interface (1ms)
✓ must correctly implement mathematical operations (5ms)
✕ must ensure the immutability of class instances (2ms)
✕ must ensure the immutability of class 2 instances (2ms)
Help me to complete the task correctly, please
My guess is that you need to return a new Calculator instance every time you do an operation:
class Calc {
constructor(num = 0) {
this.num = num;
}
add(a) {
return new Calc(this.num+a);
}
sub(a) {
return new Calc(this.num-a);
}
result() {
return this.num;
}
}