Conditional

Ternary operator

Operator is frequently used as an alternative to an if...else statement

condition ? exprIfTrue : exprIfFalse

Example

function getFee(isMember) {
  return isMember ? '$2.00' : '$10.00';
}

console.log(getFee(true));
// Expected output: "$2.00"

console.log(getFee(false));
// Expected output: "$10.00"

console.log(getFee(null));
// Expected output: "$10.00"

Conditional Chain

The ternary operator is right-associative, which means it can be "chained" in the following way, similar to an if … else if … else if … else chain

function example() {
  return condition1 ? value1
    : condition2 ? value2
    : condition3 ? value3
    : value4;
}

// equivalent to
function example() {
  if (condition1) {
    return value1;
  } else if (condition2) {
    return value2;
  } else if (condition3) {
    return value3;
  } else {
    return value4;
  }
}

Comparison

Comparing whether more than 3 elements are equal to each other?

Comparison logic for up to three elements is straightforward. Comparing more elements need more clever solutions.

/* manual comparison of 3 elements */ 
if(g === h && g === f) { "do something" } 

/* looping comparison of n-elements */ 
function nEqual(){
  for (let i = 1; i < arguments.length; i++){
    if (
        arguments[i] === null || 
        arguments[i] !== arguments[i-1]
      ) {
        return false;
      }
  return true;
};

nEqual(a,b,c,d,e,f,g,h) && { "do something" }