Error when trying to create an image in Node js

function BW(){
    let pixels=[];
    for(let i=0;i<256;i++){
        pixels.push(random(0,255))
    }
    let l=Buffer.from(pixels);
    console.log(l)
    
fs.createWriteStream('hi.png').write(l);
}
BW()

function BW(){
    let pixels=[];
    for(let i=0;i<256;i++){
        pixels.push(random(0,255))
    }
    let l=Buffer.from(pixels);
    console.log(l)
    
fs.createWriteStream('hi.png').write(l);
}
BW()