Promise 在定义嵌套 object 属性之前解析

Question

I am trying to return an object with two properties... one which is generating a blob, and requires time to resolve. However javascript seems to jump to the next function (or 'link' in the chain') before the promise is resolved. Is there any way I can make it wait for this nested property to resolve before jumping to the next function?

fetch(prefix + '/download', {
    method: 'POST',
    .....
})
.then((response) => {
    var contentDisposition = response.headers.get('content-disposition');
    var fileName = contentDisposition.split('filename=')[1].split(';')[0];
    return { blob: response.blob(), filename: fileName }
})
.then((blob) => {
    return { href: URL.createObjectURL(blob.blob), filename: blob.filename }
})

I receive Failed to execute 'createObjectURL' on 'URL': No function was found that matched the signature provided. , presumably because blob.blob returns a Promise and has no value yet.

Answer 1

Try returning the response.blob() promise with it's own then() to return the final data

fetch(prefix + '/download', {
    method: 'POST',
    .....
})
.then((response) => {
    var contentDisposition = response.headers.get('content-disposition');
    var filename = contentDisposition.split('filename=')[1].split(';')[0];

     return response.blob().then(blob =>{
        return  { href: URL.createObjectURL(blob), filename}
     });    
});