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JavaScript fetch() constantly returns Promise object, should return Number or String

P

ppowell777

Well-Known Coder
I have no idea why this is happening, but every single time I run this simple function that fetches URL content and expect a String or Number, I get a Promise object, and I can't figure out why.

JavaScript: 
/**
 * Options object based on https://stackoverflow.com/questions/41030425/disabling-cors-using-js-fetch
 */
async function checkUrl(url) {
    let text = '';
    try {
        const controller = new AbortController();
        const timeout = setTimeout(() => { controller.abort(); }, 5000);
        /*const options = {
          method: 'GET',
          mode: 'no-cors',
          signal: controller.signal
        };*/
        await fetch(url, { signal: controller.signal })
             .then((response) => {
                // BASED ON https://dmitripavlutin.com/timeout-fetch-request/ PUT clearTimeout() BEFORE THE return STATEMENT BLOCK
                clearTimeout(timeout);               
                /*if (response.status >= 200 && response.status < 400) {
                    //console.log(`GOOD response code = ${response.status}`);
                    return true;
                } else {
                    //console.log(`BAD response code = ${response.status}`);
                    return false;
                }*/
                return response.text();
             })
             .then((myText) => {
                text = myText;
             })
             .catch((e) => { return new TypeError(`Unable to obtain response code: ${e.message}`) });
    } catch (e) {
        //console.error(`Unable to run catchUrl(): ${e.message}`);
        return new TypeError(`Unable to run checkUrl(): ${e.message}`);
    }
    
    return text;
}

Can someone help me figure this out?
Thanks
 
Solution
P
I gave up on fetch() altogether and opted for jQuery.get() instead, and after trying to work with Promise objects more directly in the code, I finally got it to work, albeit being rather slow due to asynchronous functionality, but it works!

JavaScript: 
function checkResourceUrls() {
    try {
        const waitingForTable = setInterval(() => {
            if (typeof document.getElementById('resources_table') !== 'undefined' && document.getElementById('resources_table') != null) {
                clearInterval(waitingForTable);
                const anchors = Array.from(document.getElementsByTagName('A'));
                checkResourceUrlLinks(anchors);
            }
        }, 100);
    } catch (e) {
        console.error(`Unable to run...
Sort by date Sort by votes
ppowell777 said:
I have no idea why this is happening, but every single time I run this simple function that fetches URL content and expect a String or Number, I get a Promise object, and I can't figure out why.

JavaScript: 
/**
 * Options object based on https://stackoverflow.com/questions/41030425/disabling-cors-using-js-fetch
 */
async function checkUrl(url) {
    let text = '';
    try {
        const controller = new AbortController();
        const timeout = setTimeout(() => { controller.abort(); }, 5000);
        /*const options = {
          method: 'GET',
          mode: 'no-cors',
          signal: controller.signal
        };*/
        await fetch(url, { signal: controller.signal })
             .then((response) => {
                // BASED ON https://dmitripavlutin.com/timeout-fetch-request/ PUT clearTimeout() BEFORE THE return STATEMENT BLOCK
                clearTimeout(timeout);              
                /*if (response.status >= 200 && response.status < 400) {
                    //console.log(`GOOD response code = ${response.status}`);
                    return true;
                } else {
                    //console.log(`BAD response code = ${response.status}`);
                    return false;
                }*/
                return response.text();
             })
             .then((myText) => {
                text = myText;
             })
             .catch((e) => { return new TypeError(`Unable to obtain response code: ${e.message}`) });
    } catch (e) {
        //console.error(`Unable to run catchUrl(): ${e.message}`);
        return new TypeError(`Unable to run checkUrl(): ${e.message}`);
    }
   
    return text;
}

Can someone help me figure this out?
Thanks
Click to expand...
This is because you need to resolve the promise
 
Upvote 0 Downvote
Modified the code to handle the Promise object and I STILL get the Promise object back, not the URL's HTML string text

JavaScript: 
/**
 * Options object based on https://stackoverflow.com/questions/41030425/disabling-cors-using-js-fetch
 */
async function checkUrl(url) {
    let text = '';
    try {
        const controller = new AbortController();
        const timeout = setTimeout(() => { controller.abort(); }, 5000);
        /*const options = {
          method: 'GET',
          mode: 'no-cors',
          signal: controller.signal
        };*/
        await fetch(url, { signal: controller.signal })
             .then((response) => {
                // BASED ON https://dmitripavlutin.com/timeout-fetch-request/ PUT clearTimeout() BEFORE THE return STATEMENT BLOCK
                clearTimeout(timeout);               
                /*if (response.status >= 200 && response.status < 400) {
                    //console.log(`GOOD response code = ${response.status}`);
                    return true;
                } else {
                    //console.log(`BAD response code = ${response.status}`);
                    return false;
                }*/
                if (response.ok && response.status == 200) {
                    return response.text();
                } else if (response.status >= 400) {
                    return Promise.reject(new TypeError(`Returned status of ${response.status}`));
                }
             })
             .then((myText) => {
                text = myText;
             })
             .catch((e) => { return new TypeError(`Unable to obtain response code: ${e.message}`) });
    } catch (e) {
        //console.error(`Unable to run catchUrl(): ${e.message}`);
        return new TypeError(`Unable to run checkUrl(): ${e.message}`);
    }
    
    return text;
}
 
Upvote 0 Downvote
I gave up on fetch() altogether and opted for jQuery.get() instead, and after trying to work with Promise objects more directly in the code, I finally got it to work, albeit being rather slow due to asynchronous functionality, but it works!

JavaScript: 
function checkResourceUrls() {
    try {
        const waitingForTable = setInterval(() => {
            if (typeof document.getElementById('resources_table') !== 'undefined' && document.getElementById('resources_table') != null) {
                clearInterval(waitingForTable);
                const anchors = Array.from(document.getElementsByTagName('A'));
                checkResourceUrlLinks(anchors);
            }
        }, 100);
    } catch (e) {
        console.error(`Unable to run checkResourceUrls(): ${e.message}`);
    }
}

/**
 * This saved the day: https://stackoverflow.com/questions/42173350/synchronous-and-asynchronous-loops-in-javascript
 */
async function checkResourceUrlLinks(anchors) {
    try {
        let resourceId = '';
        let html = '';
        for (let anchor of anchors) {
            resourceId = (anchor.id.trim().startsWith('link_row_')) ? anchor.id.split('_')[2] : '';
            if (resourceId.trim().length > 0) {
                await new Promise(next => {
                    $.get(`${CHECKER_DEV_URL + '?url=' + encodeURIComponent(anchor.href)}`, (responseCode) => {
                        html = $(`#col1_${resourceId}`).html();
                        /**
                         * Bear in mind that the jQuery.get() asynchronous function will go tot he CMA's PHP side, to a
                         * specific URL, which will perform a PHP curl() based on the query string value being anchor.href here,
                         * perform a response status check, then return it as HTML consisting solely of the response code, which
                         * Javascript can interpret as being a Number
                         */
                        if (!isNaN(responseCode.trim()) && responseCode >= 200 && responseCode < 400) {
                            $(`#col1_${resourceId}`).html(`${html} ${GOOD_URL_INDICATOR}`);
                        } else if (!isNaN(responseCode.trim())) {
                            $(`#col1_${resourceId}`).html(`${html} ${BAD_URL_INDICATOR}`);
                        } else {
                            console.error(`Error attempting to verify "${anchor.href}" response code: ${responseCode}`);
                        }
                        
                        next();
                    });
                });
            }
        }
    } catch (e) {
        console.error(`Unable to run checkResourceUrls(anchor): ${e.message}`);
    }
}
 
Upvote 0 Downvote
Solution
ppowell777 said:
I gave up on fetch() altogether and opted for jQuery.get() instead, and after trying to work with Promise objects more directly in the code, I finally got it to work, albeit being rather slow due to asynchronous functionality, but it works!

JavaScript: 
function checkResourceUrls() {
    try {
        const waitingForTable = setInterval(() => {
            if (typeof document.getElementById('resources_table') !== 'undefined' && document.getElementById('resources_table') != null) {
                clearInterval(waitingForTable);
                const anchors = Array.from(document.getElementsByTagName('A'));
                checkResourceUrlLinks(anchors);
            }
        }, 100);
    } catch (e) {
        console.error(`Unable to run checkResourceUrls(): ${e.message}`);
    }
}

/**
 * This saved the day: https://stackoverflow.com/questions/42173350/synchronous-and-asynchronous-loops-in-javascript
 */
async function checkResourceUrlLinks(anchors) {
    try {
        let resourceId = '';
        let html = '';
        for (let anchor of anchors) {
            resourceId = (anchor.id.trim().startsWith('link_row_')) ? anchor.id.split('_')[2] : '';
            if (resourceId.trim().length > 0) {
                await new Promise(next => {
                    $.get(`${CHECKER_DEV_URL + '?url=' + encodeURIComponent(anchor.href)}`, (responseCode) => {
                        html = $(`#col1_${resourceId}`).html();
                        /**
                         * Bear in mind that the jQuery.get() asynchronous function will go tot he CMA's PHP side, to a
                         * specific URL, which will perform a PHP curl() based on the query string value being anchor.href here,
                         * perform a response status check, then return it as HTML consisting solely of the response code, which
                         * Javascript can interpret as being a Number
                         */
                        if (!isNaN(responseCode.trim()) && responseCode >= 200 && responseCode < 400) {
                            $(`#col1_${resourceId}`).html(`${html} ${GOOD_URL_INDICATOR}`);
                        } else if (!isNaN(responseCode.trim())) {
                            $(`#col1_${resourceId}`).html(`${html} ${BAD_URL_INDICATOR}`);
                        } else {
                            console.error(`Error attempting to verify "${anchor.href}" response code: ${responseCode}`);
                        }
                       
                        next();
                    });
                });
            }
        }
    } catch (e) {
        console.error(`Unable to run checkResourceUrls(anchor): ${e.message}`);
    }
}
Click to expand...
Nice! Yeah async wil always bog down performance because you're waiting for those promises to resolve
 
Upvote 0 Downvote

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