Ternary operator / Question mark and colon in JavaScript

“Question mark” or “conditional” operator in JavaScript is a ternary operator that has three operands.

  • The expression consists of three operands: the condition, value if true and value if false.
  • The evaluation of the condition should result in either true/false or a boolean value.
  • The true value lies between “?” & “:” and is executed if the condition returns true. Similarly, the false value lies after “:” and is executed if the condition returns false.

Syntax:

condition ? value if true : value if false
    condition:



  • Expression to be evaluated which returns a boolean value.

    • value if true:

  • Value to be executed if condition results in true state.

    • value if false:

  • Value to be executed if condition results in false state.

Examples:

Input: let result = (10 > 0) ? true : false;
Output: true

Input: let message = (20 > 15) ? "Yes" : "No";
Output: Yes

The following programs will illustrate conditional operator more extensively:

Program 1:

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<script>
    //JavaScript to illustrate
    //Conditional operator
  
    let age = 60
    let result = (age > 59)?
        "Senior Citizen":"Not a Senior Citizen"; 
  
    alert(result);
</script>                    

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Output:


Senior Citizen


An example of multiple conditional operators.

Program 2:











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<script> 


    //JavaScript to illustrate 


    //multiple Conditional operators 


  


    let marks = 95; 


    let result = (marks < 40) ? "Unsatisfactory" :  


             (marks < 60) ? "Average" : 


             (marks < 80) ? "Good" : "Excellent" ; 


  


    alert(result); 


</script>         



















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Output:


Excellent



          
          
          
          

            

    

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