resolve and reject in promise code example

Example 1: js create a promise

/*
	A Promise is a proxy for a value not necessarily known when the promise is created. 
    It allows you to associate handlers with an asynchronous action's eventual success 
    value or failure reason.
*/            
let promise = new Promise((resolve , reject) => {
  fetch("https://myAPI")
    .then((res) => {
      // successfully got data
      resolve(res);
    })
    .catch((err) => {
      // an error occured
      reject(err);
    });          
});

Example 2: js promise examples

//Promise to load a file...
//use with openFile(url, fCallback);
//fCallback(fileContents){ //do something with fileContents}
const loadFile = url => {
    return new Promise(function(resolve, reject) {
        //Open a new XHR
        var request = new XMLHttpRequest();
        request.open('GET', url);
        // When the request loads, check whether it was successful
        request.onload = function() {
            if (request.status === 200) {
                // If successful, resolve the promise
                resolve(request.response);
            } else {
                // Otherwise, reject the promise
                reject(Error('An error occurred while loading image. error code:' + request.statusText));
            }
        };
        request.send();
    });
};
const openFile = (url, processor) => {
    loadFile(url).then(function(result) {
            processor(result);
        },
        function(err) {
            console.log(err);
        });
};

Example 3: promise resolve reject

function testFunction(value) {
    return new Promise(function (resoleve, reject) {
        setTimeout(function () {
            let n = value;
            if (n < 100) {
                resoleve("範囲内");
            } else {
                reject("範囲外");
            }
        }, 2000);
    })
}
 
testFunction(10)
    .then(function (value) {
        console.log(value);
        return testFunction(50);
    })
    .then(function (value) {
        console.log(value);
        return testFunction(150);
    })
    .catch(function (error) {
        console.log(`エラーです。${error}`);
    })

Example 4: promise resolve reject

function testFunction() {
    return new Promise(function (resolve, reject) {
        setTimeout(function () {
            resolve('hello!');
        }, 1000);
    })
}
 
testFunction()
    .then(function (value) {
        console.log(value);
    })
    .catch(function (error) {
        console.log(error);
    })

Example 5: promise resolve reject

function testFunction(value) {
    return new Promise(function (resoleve, reject) {
        setTimeout(function () {
            let n = value;
            if(n<100){
                resoleve("範囲内");
            }else{
                reject("範囲外");
            }
        }, 2000);
    })
}
 
testFunction(1000)
    .then(function (value) {
        console.log(value);
    })
    .catch(function(error){
        console.log(`エラーです。${error}`);
    })