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JavaScript Logical AND assignment (&&=) Operator
  • Last Updated : 25 Feb, 2021

This operator is represented by x &&= y, and it is called the logical AND assignment operator. It assigns the value of y into x only if x is a truthy value.

We use this operator x &&= y like this. Now break this expression into two parts, x && (x = y).  If the value of x is truth, then the statement (x = y) executes and the value of y gets stored into x but if the value of x is a falsy value then the statement (x = y) does not get executed.

Syntax :

x &&= y

is equivalent to 

x && (x = y)

Example:



Javascript




<script>
  let name = {
    firstName: "Ram",
    lastName: "",
  };
  
  console.log(name.firstName);
  
  // Changing the value using logical
  // AND assignment operator
  name.firstName &&= "Shyam";
  
  // Here the value changed because
  // name.firstName is truthy
  console.log(name.firstName);
  
  console.log(name.lastName);
  
  // Changing the value using logical 
  // AND assignment operator
  name.lastName &&= "Kumar";
  
  // Here the value remains unchanged 
  // because name.lastName is falsy
  console.log(name.lastName);
</script>

Output :

"Ram"
"Shyam"
""
""

Example 2:

HTML




<!DOCTYPE html>
<html>
  
<body>
  <h1>Hello Geeksforgeeks</h1>
  <p id="print_arr"></p>
  
  <script>
      
      let arr = [1, 2, "apple", null, undefined, []]
        
      // Replace each truthy values with "gfg"
        
      arr.forEach((item, index)=>{
        arr[index] &&= "gfg"
    })
  
    document.getElementById("print_arr").innerText = arr.toString();
    //console.log(arr)
  </script>
    
</body>
</html>

Output :

Supported Browsers:

  • Chrome 85
  • Edge 85
  • Firefox 79
  • Safari 14

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