Javascript 图像 URL 验证 [英] Javascript Image Url Verify

问题描述

我需要验证图像 url 以检查该 url 是否是以下任何扩展名的图像:- jpeg、jpg、gif、png.示例:- 当我们验证此 url http://www.example.com/asdf.jpg 时，它应该给我们 true值和像这样的 url http://www.example.com/asdf.php 应该返回 false.我们如何在 javascript 中执行此操作，而且我想检查 url 的内容类型.这样我们就可以判断url是否是图片.

I need to verify an image url to check whether the url is an image of any of these extensions:- jpeg, jpg, gif, png. Example:- when we verify this url http://www.example.com/asdf.jpg it should give us true value and with url like this http://www.example.com/asdf.php should return false. How can we do this in javascript and also i want to check the content type of url. So that we can say whether the url is an image or not.

推荐答案

您可以使用这样的正则表达式来检查文件扩展名:

You can use a regular expression like this to check the file extension:

function checkURL(url) {
    return(url.match(/.(jpeg|jpg|gif|png)$/) != null);
}

这会检查网址是否以这四个扩展名中的任何一个结尾.

This checks to see if the url ends in any of those four extensions.

我不知道客户端中的 javascript 无法验证与网页不在同一域中的 URL 的内容类型，因为您不能在网页域之外使用 ajax.据我所知，您必须将 URL 发送到服务器进程并让它下载图像、获取内容类型并将其返回给您.

I know of no way from javascript in the client to verify the content-type of a URL that isn't on the same domain as the web page because you can't use ajax outside of the domain of the web page. As best I know, you'd have to ship the URL to a server process and have it download the image, get the content type and return that to you.

但是，您可以使用如下函数检查图像标签是否可以加载 URL:

But, you can check to see if an image tag can load the URL by using a function like this:

function testImage(url, callback, timeout) {
    timeout = timeout || 5000;
    var timedOut = false, timer;
    var img = new Image();
    img.onerror = img.onabort = function() {
        if (!timedOut) {
            clearTimeout(timer);
            callback(url, "error");
        }
    };
    img.onload = function() {
        if (!timedOut) {
            clearTimeout(timer);
            callback(url, "success");
        }
    };
    img.src = url;
    timer = setTimeout(function() {
        timedOut = true;
        // reset .src to invalid URL so it stops previous
        // loading, but doesn't trigger new load
        img.src = "//!!!!/test.jpg";
        callback(url, "timeout");
    }, timeout); 
}

此函数将在未来某个时间调用您的回调，并带有两个参数:原始 URL 和结果(成功"、错误"或超时").你可以在几个 URL 上看到这项工作，有好有坏，在这里:http://jsfiddle.net/jfriend00/qKtra/

This function will call your callback at some future time with two arguments: the original URL and a result ("success", "error" or "timeout"). You can see this work on several URLs, some good and some bad, here: http://jsfiddle.net/jfriend00/qKtra/

而且，由于现在是 Promises 的时代，这里有一个返回 Promise 的版本:

And, since this is now the era of Promises, here's a version that returns a promise:

function testImage(url, timeoutT) {
    return new Promise(function (resolve, reject) {
        var timeout = timeoutT || 5000;
        var timer, img = new Image();
        img.onerror = img.onabort = function () {
            clearTimeout(timer);
            reject("error");
        };
        img.onload = function () {
            clearTimeout(timer);
            resolve("success");
        };
        timer = setTimeout(function () {
            // reset .src to invalid URL so it stops previous
            // loading, but doesn't trigger new load
            img.src = "//!!!!/test.jpg";
            reject("timeout");
        }, timeout);
        img.src = url;
    });
}

还有一个 jsFiddle 演示:http://jsfiddle.net/jfriend00/vhtzghkd/

And, a jsFiddle demo: http://jsfiddle.net/jfriend00/vhtzghkd/

这篇关于Javascript 图像 URL 验证的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！