How to eliminate if-else when doing different things according to different combinations of boolean value?

Question

for example, suppose I need to do different things according to combinations of boolean values: cond_0,cond_1 and cond_2 :

cond_0 cond_1 cond_2
false  false  false  a();
false  false  true   b();
.
.
.
true   true   true   h();

it looks as if mapping bit numbers to functions:

000:a()
001:b()
.
.
.
111:h()

while the general rule looks like very simple, I don't know how to write it without if-else, and the current form looks like that:

var f=function(cond_0,cond_1,cond_2){
  if(!cond_0 && !cond_1 && !cond_2){
    a();
  }else if( cond_0 && !cond_1 && !cond_2)){
    b();
  }else if(!cond_0 &&  cond_1 && !cond_2)){
    c();
  }else if( cond_0 &&  cond_1 && !cond_2)){
    d();
  }else if(!cond_0 && !cond_1 &&  cond_2)){
    e();
  }else if( cond_0 && !cond_1 &&  cond_2)){
    f();
  }else if(!cond_0 &&  cond_1 &&  cond_2)){
  g();
  }else if( cond_0 &&  cond_1 &&  cond_2)){
    h();
  }
}

which is very long and hard to read. And when a new boolean condition cond_3 is added, it is horrible to modify the code:

if(!cond_0 && !cond_1 && !cond_2 && !cond_3){
    a();
  }else if( cond_0 && !cond_1 && !cond_2 !cond_3)){
    b();
  }
  .
  .
  .

Is there any way to eliminate the if else, so that cond_0 , cond_1 and cond_2 can just appear once only inside the function, and also easy to add new function when cond_3 is added? I want something like:

var f=function(cond_0,cond_1,cond_2){
  var magic=(000:a,001:b,010:c...);
  magic(cond_0,cond_1,cond_2)();
}

Answer 1

See this implementation. Here all the three parameters (boolean expected) are multiplied by their place values to form the number and then padded with '0' to the desired length. This value is searched for in the magic object and the function if defined is called.

var a = function() {
  console.log('a() called');
};
var b = function() {
  console.log('b() called');
};
var c = function() {
  console.log('c() called');
};

var f = function(cond_0, cond_1, cond_2) {
  var cond = ((cond_0 * 100) + (cond_1 * 10) + (cond_2)).toString().padStart(3, '0');
  var magic = {
    '000': a,
    '001': b,
    '010': c
  };
  if (typeof magic[cond] === 'function') {
    magic[cond]();
  } else {
    console.log('No function defined for this cond');
  }
}

f(false, false, false);
f(false, false, true);
f(false, true, false);
f(true, false, false);