Resize base64 image and get the return value out of the function in nodejs-CodePudding

async function imgResize(data){
// Convert base64 to buffer => <Buffer ff d8 ff db 00 43 00 ...
const buffer = Buffer.from(data, "base64");
Jimp.read(buffer, (err, res) => {
    if (err) throw new Error(err);
    console.log("Original image size: " res.getWidth() "x" res.getHeight())
    if (res.getWidth() > 1025){
        res.resize(1025, Jimp.AUTO)
        console.log("resized image size: " res.getWidth() "x" res.getHeight())
     }
    res.getBase64(Jimp.AUTO, (err, value)=>{
        if(err){return err)}
        return value;
    })
}
const img =  await imgResize(base64data)

I get, SyntaxError: await is only valid in async functions and the top level bodies of modules. But if I remove the async and just print the value without returning it, it works fine. So how I will able to get the value out of that function as return value and hold it in a variable?

CodePudding user response：

You can't return values inside an asynchronous callback and expect them to be assigned to a variable. Asynchronous callbacks are executed at a later point in time by Node.js at which point the execution context is lost. For example, this won't work:

function getImageWidth(buffer) {
  Jimp.read(buffer, (err, res) => {
    // Outside context is lost and returning here doesn't
    // affect the return value of `getImageWidth` parent function
    return res.getWidth(); // won't work