JS chaining functions

Question

I'm writing a function that should work like this:

checker(3).equals(3) // true
checker(3).not().equals(3) // false
checker(3).not().equals(4) // true
checker(3).not().not().equals(4) // false

The code I came up with:

function checker(num) {
  let number = num
  return {
    not() {
      number = !number
      return this
    },
    equals(nmb) {
      return number === nmb
    }
  }
}

I can't wrap my head around what should not() do so as to make checker(num) work as it is supposed to.

Chris Li · Accepted Answer · 2019-12-06 14:40:50Z

4

You can add another boolean property that changes how equals works depending on it's value.

function checker(num) {
  let number = num
  let not = false
  return {
    not() {
      not = !not
      return this
    },
    equals(nmb) {
      return not ? number !== nmb : number === nmb
    }
  }
}

console.log(checker(3).equals(3)) // true
console.log(checker(3).not().equals(3)) // false
console.log(checker(3).not().equals(4)) // true
console.log(checker(3).not().not().equals(4)) // false

answered Dec 6, 2019 at 14:40

Chris Li

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1 Comment

FZs Over a year ago

You could replace not ? number !== nmb : number === nmb with (number === nmb) !== not

Paulo Künzel · Accepted Answer · 2019-12-06 14:42:30Z

3

Maybe somthing like this:

function checker(num) {
  let number = num
  let beTrue = true;
  return {
    not() {
      beTrue = !beTrue;
      return this
    },
    equals(nmb) {
      return (number === nmb) === beTrue;
    }
  }
}

It seems to fullfil your requirements. Hope it helps

answered Dec 6, 2019 at 14:42

Paulo Künzel

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Comments

Thomas Junk · Accepted Answer · 2019-12-06 14:52:46Z

2

An ES6 approach

const checker=(number, negate)=>{
    const neg = negate || false;
  return {
    not(){
        return checker(number, !neg);
    }, 
    equals(number2){
        if (neg) return number != number2;
      return number == number2;
    }
  }
}

what should not() do so as to make checker(num) work as it is supposed to.

not could return a new checker.

answered Dec 6, 2019 at 14:52

Thomas Junk

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Comments

MikNiller · Accepted Answer · 2019-12-06 14:41:45Z

1

I think i would let the notfunction control the operator, something like

function checker(num) {
  let operator = 'equals'; 
  let number = num
  return {
    not() {
      if(operator==='equals')    
         operator = 'not equals'; 
      else 
          operator = 'equals'; 
      return this
    },
    equals(nmb) {
      if(operator==='equals')  
         return number === nmb
      else 
        return number !== nmb
    }
  }
}

just using a string as operator for clarity, a proberly better solution could be to use a boolean or number value

answered Dec 6, 2019 at 14:41

MikNiller

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