get_airtable_schema.js

// Go to https://airtable.com/api and select a base. 
// Then open your browsers console (Ctrl+Alt+I) and run the following code.

var myapp = {
    id:window.application.id,
    name:window.application.name,
    tables:[]
};
for (let table of window.application.tables){
    var mytable = {
            id:table.id,
            isEmpty:table.isEmpty,
            name:table.name,
            nameForUrl:table.nameForUrl,
            primaryColumnName:table.primaryColumnName,
            columns:[]
    };
    for (let column of table.columns){
        var mycolumn = {
            id:column.id,
            name:column.name,
            type:column.type,
            typeOptions:column.typeOptions
        };
        mytable.columns.push(mycolumn);
    }
    myapp.tables.push(mytable);
}
jQuery('link[rel=stylesheet]').remove();
jQuery("body").html(JSON.stringify(myapp));
console.log(myapp);

This code no longer seems to work since window.application is undefined?

My bad, I wasn't running it while looking at the API docs but when I was viewing the base. It works great!