addeventlistener - How to pass information from parent window to child window without query string in JavaScript?

Question

I am looking to pass information from a parent window to a child window, but cannot use a query string because there is too much information and the pop-up gets blocked. They have different domains. (cross-origin) How would I achieve this? I want the information to be passed as soon as the child window is open (the JavaScript is loaded)

Answer 1

Posting an "I am ready" message should work.

Parent:

var child = window.open(childURL);
window.addEventListener("message",(e)=>{
    if(e.data == "ready")
    {
        e.source.postMessage("some data for you","*");
    }
})

Child:

window.addEventListener("load",()=>{
    window.opener.postMessage("ready","*");
})
window.addEventListener("message",(e)=>{
    console.log(e.data);
});