dongqin5604
dongqin5604
2019-03-01 20:12

使用ajax(javascript)监视文本文件中的更改

I have done my research and cannot find an answer that works on this topic. I have a webpage right now with a text input field, every time that the input is changed it runs a function that writes data to a text file. The problem is that when I try to read the file and change an elements contents to the text file's contents, it always returns the same value. My function returns a value that my text file was a long while ago. Here is my code:

function OpenFile(filePath) {
    var text = "NULL";
    var ajax = new XMLHttpRequest();
    ajax.onreadystatechange = function() {
        if (ajax.readyState == 4) {
            text = ajax.responseText;
        }
    };
    ajax.open("POST", filePath, false);
    ajax.send();
    return text;
}

function WriteFile(filePath, content){
    var formdata = new FormData();
    formdata.append("content", content);
    var ajax = new XMLHttpRequest();
    ajax.open("POST", filePath);
    ajax.onreadystatechange = function() {
        if(ajax.status == 200 && ajax.readyState == 4) {
            
        }
    };
    ajax.send(formdata);
}

Is there anything wrong with my code that prevents me from reading the current contents of my file?

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1条回答

  • dongshi2836 dongshi2836 2年前

    The file may be cached by the browser's HTTP cache. Try appending a randomly-generated number as a query parameter to your request (your filePath variable).

    For example,

    function OpenFile(filePath) {
        var text = "NULL";
        var ajax = new XMLHttpRequest();
        ajax.onreadystatechange = function() {
            if (ajax.readyState == 4) {
                text = ajax.responseText;
            }
        };
    
        // HERE, append the query parameter with random number
        ajax.open("POST", filePath + '?' + Math.random(), false);
    
        ajax.send();
        return text;
    }
    

    If that was the problem, then see here on more questions on how to manage clearing caches.

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