Using javascript is there a way to tell if a resource is available on the server? For instance I have images 1.jpg - 5.jpg loaded into the html page. I'd like to call a JavaScript function every minute or so that would roughly do the following scratch code...
if "../imgs/6.jpg" exists:
var nImg = document.createElement("img6");
nImg.src = "../imgs/6.jpg";
Thoughts? Thanks!
You could use something like:
function imageExists(image_url){
var http = new XMLHttpRequest();
http.open('HEAD', image_url, false);
http.send();
return http.status != 404;
}
Obviously you could use jQuery/similar to perform your HTTP request.
$.get(image_url)
.done(function() {
// Do something now you know the image exists.
}).fail(function() {
// Image doesn't exist - do something else.
})
You can just check if the image loads or not by using the built in events that is provided for all images.
The onload and onerror events will tell you if the image loaded successfully or if an error occured :
var image = new Image();
image.onload = function() {
// image exists and is loaded
document.body.appendChild(image);
}
image.onerror = function() {
// image did not load
var err = new Image();
err.src = '/error.png';
document.body.appendChild(err);
}
image.src = "../imgs/6.jpg";
A better and modern approach is to use ES6 Fetch API to check if an image exists or not:
fetch('https://via.placeholder.com/150', { method: 'HEAD' })
.then(res => {
if (res.ok) {
console.log('Image exists.');
} else {
console.log('Image does not exist.');
}
}).catch(err => console.log('Error:', err));
Make sure you are either making the same-origin requests or CORS is enabled on the server.
If anyone comes to this page looking to do this in a React-based client, you can do something like the below, which was an answer original provided by Sophia Alpert of the React team here
getInitialState: function(event) {
return {image: "http://example.com/primary_image.jpg"};
},
handleError: function(event) {
this.setState({image: "http://example.com/failover_image.jpg"});
},
render: function() {
return (
<img onError={this.handleError} src={src} />;
);
}
Basicaly a promisified version of @espascarello and @adeneo answers, with a fallback parameter:
const getImageOrFallback = (path, fallback) => {
return new Promise(resolve => {
const img = new Image();
img.src = path;
img.onload = () => resolve(path);
img.onerror = () => resolve(fallback);
});
};
// Usage:
const link = getImageOrFallback(
'https://www.fillmurray.com/640/360',
'https://via.placeholder.com/150'
).then(result => console.log(result) || result)Edit march 2021
After a conversation with @hitautodestruct I decided to add a more "canonical" version of the Promise based function. onerror case is now being rejected, but then caught and returning a default value:
function getImageOrFallback(url, fallback) {
return new Promise((resolve, reject) => {
const img = new Image()
img.src = url
img.onload = () => resolve(url)
img.onerror = () => {
reject(`image not found for url ${url}`)
}
}).catch(() => {
return fallback
})
}
getImageOrFallback("https://google.com", "https://picsum.photos/400/300").then(validUrl => {
console.log(validUrl)
document.body.style.backgroundImage = `url(${validUrl})`
})html, body {
height: 100%;
background-repeat: no-repeat;
background-position: 50% 50%;
overflow-y: hidden;
}Note: I may personally like the fetch solution more, but it has a drawback – if your server is configured in a specific way, it can return 200 / 304, even if the file doesn't exist. This, on the other hand, will do the job.
You may call this JS function to check if file exists on the Server:
function doesFileExist(urlToFile)
{
var xhr = new XMLHttpRequest();
xhr.open('HEAD', urlToFile, false);
xhr.send();
if (xhr.status == "404") {
console.log("File doesn't exist");
return false;
} else {
console.log("File exists");
return true;
}
}
You can do this with your axios by setting relative path to the corresponding images folder. I have done this for getting a json file. You can try the same method for an image file, you may refer these examples
If you have already set an axios instance with baseurl as a server in different domain, you will have to use the full path of the static file server where you deploy the web application.
axios.get('http://localhost:3000/assets/samplepic.png').then((response) => {
console.log(response)
}).catch((error) => {
console.log(error)
})
If the image is found the response will be 200 and if not, it will be 404.
Also, if the image file is present in assets folder inside src, you can do a require, get the path and do the above call with that path.
var SampleImagePath = require('./assets/samplepic.png');
axios.get(SampleImagePath).then(...)
If you are using React try this custom Image component:
import React, { useRef } from 'react';
import PropTypes from 'prop-types';
import defaultErrorImage from 'assets/images/default-placeholder-image.png';
const Image = ({ src, alt, className, onErrorImage }) => {
const imageEl = useRef(null);
return (
<img
src={src}
alt={alt}
className={className}
onError={() => {
imageEl.current.src = onErrorImage;
}}
ref={imageEl}
/>
);
};
Image.defaultProps = {
onErrorImage: defaultErrorImage,
};
Image.propTypes = {
src: PropTypes.string.isRequired,
alt: PropTypes.string.isRequired,
className: PropTypes.string.isRequired,
onErrorImage: PropTypes.string,
};
export default Image;
You can refer this link for check if a image file exists with JavaScript.
checkImageExist.js:
var image = new Image(); var url_image = './ImageFolder/' + variable + '.jpg'; image.src = url_image; if (image.width == 0) { return `<img src='./ImageFolder/defaultImage.jpg'>`; } else { return `<img src='./ImageFolder/`+variable+`.jpg'`; } } ```
