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<title>Promises</title> <script src="plugins/traceur-compiler/bin/traceur.js"></script> <script src="plugins/traceur-compiler/src/bootstrap.js"></script> <script> traceur.options.experimental = true; </script> <script type="module">//# Basic promise usage
//This is how the basic mechanism works.
//Create a new Promise with resolve and reject parameters.
//Call those parameters when a condition is met, or fails to be met
let promise = new Promise((resolve, reject) => {
let x = 10;
//Try changing x to another number to see what happens when it's rejected
if (x === 10) {
resolve("promise resolved");
} else {
reject("promise rejected");
}
});
promise.then( (resolve) => { console.log(resolve); }, (reject) => { console.log(reject); } );
//# Using a promise with XHR
let rooms = {};
//Create the promise let loadingPromise = new Promise((resolve, reject) => { let xhr = new XMLHttpRequest(); xhr.open("GET", "rooms.json", true); xhr.responseType = 'text'; xhr.onload = (event) => { if (xhr.status === 200) { rooms = JSON.parse(xhr.responseText); resolve("JSON data loaded"); } else { reject("The JSON file didn't load"); } }; xhr.send(); });
//Use the promise loadingPromise.then( (resolve) => { console.log(resolve); //Displays: JSON data loaded }, (reject) => { console.log(reject); //Displays: The JSON file didn't load } );
</script>