Why is my boolean value not changing? Is something wrong with my fucntion callbacks?

I am trying to make a rock, paper scissor console game with JS but only first testing the waters with rock and scissor. I have a function that takes in a randomly generated value from an array and then asks the user for their input and them compares the two values. the "win" variable determines if a winner is declared or not with help of check_winner() function. But my boolean value for win always remains false.

Here's the code:

var arr = ['rock', 'scissor']
let win = false

function play(arr){
    var b = arr[(Math.floor(Math.random()*2))]
    console.log(b)
    var a = prompt('Enter choice:')
    console.log(a)

    
      do{

        if(a==="rock" && b==="scissor"){
          console.log("Rock crushes Scissor! You win bitch!") 
          win=true
        }
    
        else if(b==="rock" && a==="scissor"){
          console.log("Rock crushes Scissor! You lose bitch!") 
          win=true
        }


      }
      while(win=false);

      
    check_winner(win)
        

    }



function check_winner(win){
  if(win===true){
    console.log("gamne over")
  }
  else{
    prompt("Enter again")
  }
}

play(arr)