i'm trying to find a solution to this exercise:
Implement the calculate function that adds an object that gives the ability to do the four mathematical operations (addition, subtraction, multiplication and division) on the same number and finally print out the result.
function calculate() {
}
const calculator = calculate();
calculator.add(2).add(4).multiply(3).sub(1).sub(3).divide(2).printResult(); // result will be: 7
console.log(calculator)
so, what is the right way to solve this (and if you can add comment will be appreciated
no need to put so many this and function...
in this way you have a closure value.
=> calc_00.val = 20;
will not change the result (it just add a new property if jso is not freeze )
or throw an error in strict mode
"use strict";
function calculate( initVal = 0 ) // default value is zero
{
let
val = initVal // closure value
, jso =
{ add(v) { val += v; return this }
, sub(v) { val -= v; return this }
, multiply(v) { val *= v; return this }
, divide(v) { val /= v; return this }
, printResult() { return val }
}
Object.freeze(jso)
return jso
}
const
calc_00 = calculate()
, calc_10 = calculate(10)
;
// calc_00.yop = ()=>null; // Uncaught TypeError: can't define property "yop": Object is not extensible
// calc_00.sub = ()=>null; // Uncaught TypeError: "sub" is read-only
// calc_00.val = 20; // Uncaught TypeError: can't define property "val": Object is not extensible
calc_00.add(2).add(4).multiply(3).sub(1).sub(3).divide(2);
calc_10.add(10).multiply(3);
console.log( calc_00.printResult(), calc_10.printResult() ) // 7 , 60You can return the object itselft.
function calculate() {
return {
result: 0,
add: function(num) {
this.result += num;
return this;
},
sub: function(num) {
this.result -= num;
return this;
},
multiply: function (num) {
this.result *= num;
return this;
},
divide: function (num) {
this.result /= num;
return this;
},
printResult: function () {
return this.result;
}
}
};
const calculator = calculate();
const result = calculator.add(2).add(4).multiply(3).sub(1).sub(3).divide(2).printResult(); // result will be: 7
console.log(result);Make sure to understand how this works in JavaScript. For instance, using functions is different than using arrow functions.
Reference: JavaScript this
Alternative solution using closure
function calculate() {
let result = 0;
return {
add: function(num) {
result += num;
return this;
},
sub: function(num) {
result -= num;
return this;
},
multiply: function (num) {
result *= num;
return this;
},
divide: function (num) {
result /= num;
return this;
},
printResult: function () {
return result;
}
}
};
const calculator = calculate();
const result = calculator.add(2).add(4).multiply(3).sub(1).sub(3).divide(2).printResult(); // result will be: 7
console.log(result);