在不使用 XMLHttpRequest 的情况下检查服务器上是否存在文件

Question

Is there a quicker solution to checking if a file exists on a server? I am currently using this approach which seems pretty common on here but it is extremely slow.

            async checkFileExist(path, timeout = 200000)
        {
            let totalTime = 0;
            let checkTime = timeout / 10;
            var self = this;

            return await new Promise((resolve, reject) => {
                const timer = setInterval(function () {

                    totalTime += checkTime;

                    let fileExists = self.fileExist(path);

                    if (fileExists || totalTime >= timeout) {
                        clearInterval(timer);

                        resolve(fileExists);

                    }
                }, checkTime);
            })
        },
        fileExist(urlToFile) {
            var xhr = new XMLHttpRequest();
            xhr.open('HEAD', urlToFile, false);
            xhr.send();

            if(xhr.status == "404") {
                return false;
            } else {
                return true;
            }
        },

Mount function for component.

        mounted() {
        alert('1st test')
        var self = this
        this.checkFileExist(this.filedir).then(function (response) {
            console.log("Success!", response);
            self.loadingFile = false;
            self.renderPage(this.pageNum);
            alert('2nd test')
        }, function (error) {
            console.error("Failed!", error);
        })
    },

Answer 1

That won't tell you if a file exists. It will tell you if a URL finds a resource. It's an important distinction since a URL could be handled by server-side code and not a simple static file, while a file might exist and not have a URL.

Making an HTTP request is the simplest way to find out if a URL finds a resource. There are other ways to make HTTP requests (such as the fetch API), but they aren't faster, just different.

A potentially faster (but much more complicated) way would be to use a Websocket. You need to have it open before you wanted to know if the URL exists (otherwise any time savings are lost to establishing the Websocket connection) and you'd need to write the server side code which reacted to the Websocket message by working out if the desired URL existed and telling the client.