javascript conditional logical operator

Question

I have the following:

var cond1 = (a>b) ? true: false;
var cond2 = (d<c) ? true: false;
var cond3 = (e==f) ? true: false;

var found = cond1 && cond2 && cond3;

I want to be able in an elegant way to substitute the && logical operator for another like || and do this programmatically, as in a sort of "variable" operator. Because I don't want to do something like:

var found1 = cond1 && cond2 && cond3;
var found2 = cond1 || cond2 || cond3;
var found3 = (cond1 && cond2) || cond3;

and then switch/if depending on what choice the user has selected from the interface, it's not elegant.

How can I do this ? (if possible)

Thank you in advance

I would start doing just what I need such as var cond1 = a > b; and finally || is as much operator as && is, substitute one for another definatelly does not make your code more elegant. — Philippe Gioseffi
– Philippe Gioseffi, Commented Jun 21, 2018 at 15:45
So you want a function like CheckConditions that takes operators as parameters and compares cond1,2,3? So your found variables could be found1 = CheckConditions('&&', '&&')? — IrkenInvader
– IrkenInvader, Commented Jun 21, 2018 at 15:47
the ternary operator is unnecessary. var cond1 = a > b will give exactly the same result as var cond1 = a > b ? true : false. the result of expression a>b is already true or false. — Félix Brunet
– Félix Brunet, Commented Jun 21, 2018 at 16:14

Jamiec · Accepted Answer · 2018-06-22 08:12:06Z

2

I would start with something like a method which can take a string (AND/OR) and an array of bool delegates and perform the action(s)

function operator(which, ...args)
{
    switch(which.toUpperCase())
    {
        case "AND": return args.every(a => a());
        case "OR": return args.some(a => a());
        default: throw "Invalid operator " + which;
    }
}

var a = 1;
var b = 2;
var c = 3;
var d = 4;
var e = 5;
var f = 5;

var cond1 = () => (a>b) ;
var cond2 = () => (d<c) ;
var cond3 = () => (e==f);

var found1 = operator("and",cond1,cond2,cond3);
var found2 = operator("or",cond1,cond2,cond3);
var found3 = operator("or", () => operator("and",cond1,cond2), cond3);
console.log(found1,found2,found3)

From there its easy enough to build up dynamically.

References

edited Jun 22, 2018 at 8:12

answered Jun 21, 2018 at 15:51

Jamiec

136k15 gold badges142 silver badges202 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Jamiec Over a year ago

@ManosKounelakis It wasnt at first, I missed the tag but have updated the answer since then

MirrorMirror Over a year ago

@Jamiec I am not sure I understand where the a => a() comes from in the operator function.I suppose it's the function that is run by the .some / .every ?

Jamiec Over a year ago

@MIrrorMirror it represents the individual functions you pass in to the function. You could just do some(a) but I thought that would be less clear than .some(a => a())

Hriday Modi · Accepted Answer · 2018-06-21 16:52:12Z

1

I think elegant way of writing this is code should be readable and easy to understand. Making a logic complex to achieve simple thing doesn't make sense in my opinion. Things which kept simple and clean is less bug prone than complex logic, it gives us the confidence on our code.

Here you can store && and || in variable and can pass to the function.

var cond1 = (2>3);
var cond2 = (5<9);
var cond3 = (5==7);

const compareConditions = (operator, operand1, operand2) => {
  switch(operator){
    case "&&": {
      return operand1 && operand2;
    }
    case "||":{
       return operand1 || operand2;
    }
    default:{
      return false;
    }
  }
}

console.log(compareConditions("||", compareConditions("&&" , cond1, cond2), cond3));

answered Jun 21, 2018 at 16:52

Hriday Modi

2,08916 silver badges22 bronze badges

2 Comments

Raymond Chen Over a year ago

However this does not preserve the short-circuit behavior of the logical operators.

Hriday Modi Over a year ago

Yes, It doesn't.

Chris Disley · Accepted Answer · 2018-06-21 15:48:33Z

0

Depending on complexity, I'd either go with something similar to what you already have, or if there are a lot of options, I might go with some sort of flags/bitmask solution.

There are some good examples of this in JavaScript here:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators

answered Jun 21, 2018 at 15:48

Chris Disley

1,36318 silver badges31 bronze badges

Collectives™ on Stack Overflow

javascript conditional logical operator

3 Answers 3

3 Comments

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related