Deprecated features ](/en-US/docs/Web/JavaScript/Reference/Deprecated_and_obsolete_features)

##  In this article

  * Try it 
  * Syntax 
  * Description 
  * Examples 
  * Specifications 
  * Browser compatibility 
  * See also 

#  Left shift assignment (<<=)

The **left shift assignment (` <<= ` ) ** operator performs [ left shift
](/en-US/docs/Web/JavaScript/Reference/Operators/Left_shift) on the two
operands and assigns the result to the left operand.

##  Try it

##  Syntax

js

    
    
    x <<= y
    

##  Description

` x <<= y ` is equivalent to ` x = x << y ` , except that the expression ` x `
is only evaluated once.

##  Examples

###  Using left shift assignment

js

    
    
    let a = 5;
    // 00000000000000000000000000000101
    
    a <<= 2; // 20
    // 00000000000000000000000000010100
    
    let b = 5n;
    b <<= 2n; // 20n
    

##  Specifications

Specification  
---  
[ ECMAScript Language Specification  
#  sec-assignment-operators  ](https://tc39.es/ecma262/multipage/ecmascript-
language-expressions.html#sec-assignment-operators)  
  
##  Browser compatibility

BCD tables only load in the browser  with JavaScript enabled. Enable
JavaScript to view data.

##  See also

  * [ Assignment operators in the JS guide ](/en-US/docs/Web/JavaScript/Guide/Expressions_and_operators#assignment_operators)
  * [ Left shift ( ` << ` ) ](/en-US/docs/Web/JavaScript/Reference/Operators/Left_shift)

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