window.onload with addicional feature to support pjax

onload.js

/**
* feature: function `f` only execute once.

* @param function `f`
* @param string `id`  for debug
*/
function addOnload(f, id) {
    // to prevent f excute twice, as f is registered to both onload and 'pjax:ready'
    f.n = 1;
    
    
    var o = window.onload, F = function () {
        id && console.log(`[ want to run ${id}`)
        if (f.n) {
            f();
            id && console.log(` ]. runed ${id}`)
        }
        f.n = 0
    };
    
    // solution from: https://stackoverflow.com/questions/3698200/window-onload-vs-document-ready/19846508#19846508
    "function" != typeof o ? window.onload = F : window.onload = function () {
        o && o(), F() 
    }
    
    // event `pjax:content` is not approprate. If F registered with that event, F not executed until next page load.
    document.addEventListener('pjax:ready', F, {once:1});
}