Before I moved in how did I know the importance of Right-associative? let's dive into what is associative in short:

Associative in JavaScript:

Associative in JavaScript describes in which order the operators with the same precedence level are evaluated in an expression.

There are two types of Associative:

Left Associative:

• Operators with the left associativity are evaluated from left to right.

• when there are multiple operators with the same precedence then the expression is evaluated from left to right, one such example is with the addition and subtraction operator.

    let result = 10 + 5 - 3; 
    console.log(result);// result = 12
    // + and - operator has the same precedence, and due to their 
    // left associative nature they are evaluated as (10 + 5) - 3
  

• Another example is with is less than or greater than operator:

    console.log(2 > 3 > 5); //output: true
    //under the hood  console.log((2 >  3) > 5); within next step
    //it goes like this console.log(true > 5);
    // where true is coerced into a number value which is  1,
    //so 1  > 5 is true.
  

• Other prime examples include the OR and AND operators, waiting for your exploration!

Right Associative:

• Operators with the Right associativity are evaluated from Right to left.

• when there are multiple operators with the same precedence then the expression is evaluated from right to left, one such example is the assignment operator:

    let a = 10;
    //where the value 10 is read first & is assigned to the variable name "a".
  

Another example is the ternary operator through which I learned the importance of it.

let ternary = true;
const result = (ternary === true ? true 
: ternary === false ? "nested-true" : "nested-false");
console.log(result);

Now, let's dive under the hood to learn how the evaluation of the above expression takes place in the JavaScript engine:

On the Default Mode (Right-associative):

//Example 1
let ternary = true;
const result = (ternary === true ? true 
:(ternary === false ? "nested-true": "nested-false"));
console.log(result);

• First, the right expression (ternary === false ? "nested-true": "nested-false") is executed, and the expression is evaluated to "nested-false" as the condition "ternary === false" is false.

• Then the expression becomes like this:

    let ternary = true;
    const result = (ternary === true ? true : nested-false );
    console.log(result);
  

• Now the expression is evaluated to "true" as the condition "ternary === true" is true.

so, the final output of the above expression (Example 1) is "true".

What if the Ternary operator was left-associative?

//Example 2
let ternary = true;
const result2 = ( (ternary === true ? true : ternary === false)
 ? "nested-true": "nested-false");
console.log(result2);

• In this example 2, the (ternary === true ? true : ternary === false) is executed firstly which evaluates to "true" as the condition "ternary === true" is true.

• Then the expression becomes like this:

    //Example 2
    let ternary = true;
    const result2 = (true ? "nested-true": "nested-false");
    console.log(result2);
  

• Now, the expression is evaluated as "nested-true".

so, the final output of the above expression (Example 2) is "nested-true".

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NOTE: In example 2, the left-associative has changed the order in which the expressions are evaluated which results in neglecting the ternary === false condition and directly results in the conclusion of nested-true as the final output.

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This is the reason why the right associative nature of the ternary operator enables it for conditional chains which are concise and can be used as a replacement for if … else if … else if … else chain.

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I hope this blog provided insight into how right associativity enables conditional chains in the ternary operator. Thanks for reading! Like and subscribe for more JavaScript insights!

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