JS
CALLBACK FUNCTION - A SIMPLE EXAMPLE
DO AJAX CALLS function main (target) { for (let t of target) { fetch(t.url) .then((res) => { return res.text(); }) .then((txt) => { t.callback(txt); }); }}
THE "MAIN" FUNCTION
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OUTPUT TO CONSOLE function callbackA (res) { console.log(res); }
THE CALLBACK FUNCTIONS
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APPEND TO HTML BODY function callbackB (res) { document.body.innerHTML = res; }
CALLBACK - WHEN WE PASS A FUNCTION INTO A FUNCTION main([ { url: "PAGEA", callback: callbackA }, { url: "PAGEB", callback: callbackB } ]);
WHAT IS A CALLBACK? (A)
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CALLBACK FUNCTION GETS CALLED INSIDE THE MAIN FUNCTION * callbackA() will output AJAX fetch results into console. * callbackB() will output AJAX fetch results into HTML.
WHAT IS A CALLBACK? (B)
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