javascript - How does js determine that all resources on the page have been loaded?

Question

Make a progress bar and it will be 100% after loading. How to judge that the loading is complete?

Answer 1

Fake loading is usually done by adding random numbers, up to 99, and after all resources are loaded, it becomes 100.

Answer 2

Need a resource pool object

{
    js: [a.js,b.js],
    img:[c.png, d.jpg],
    css:[e.css]
}

Preload the files, listen to the onload event, and trigger the callback
Count the total number of files: all_files current cur_files
Percentage: percent = all_files, cur_files.

There is a ready-made loading library~ Go and find it on github.