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JavaScript Conditional Statements

المعرفة:: JavaScript
الحالة:: ملاحظة_مؤرشفة
المراجع:: JavaScript Essential Training

Conditional statements

If else

if (everydayPack.lidOpen) {  
    console.log("Lid is open!™);  
} else {  
    console.log("Lid is closed :(");  
}

Ternary Operator

The conditional (ternary) operator is the only JavaScript operator that takes three operands: a condition followed by a question mark (?), then an expression to execute if the condition is truthy followed by a colon (:), and finally the expression to execute if the condition is falsy. This operator is frequently used as a shortcut for the if statement.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_Operator 

// condition ? exprIfTrue : exprIfFalse  
everydayPack.lidOpen ? "open" : "closed";  

var age = 26;  
var beverage = age >= 21 ? "Beer" : "Juice";  
console.log(beverage); // "Beer"  

// Handling null values  
// One common usage is to handle a value that may be null  
let greeting = person => {  
  let name = person ? person.name : `stranger`;  
  return `Howdy, ${name}`;  
};  
console.log(greeting({ name: `Alice` })); // "Howdy, Alice"  
console.log(greeting(null)); // "Howdy, stranger"

Conditional chains

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; }  
}
Last update : August 14, 2023
Created : August 23, 2022

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