In Web Applications, Reading local files in browsers is not common behavior. Web Front End Developers can use this behavior to simulate the provision of Web Back End data. Then, we can implement parallel development of Web Front End and Web Back End. The development efficiency will also be improved.

The following code is about reading and writing local files in IE.

function readFileInIE(filePath) {
try {
var fso = new ActiveXObject("Scripting.FileSystemObject");

var file = fso.OpenTextFile(filePath, 1);

var fileContent = file.ReadAll();

file.Close();

return fileContent;
} catch (e) {
if (e.number == -2146827859) {
            alert('Unable to access local files due to browser security settings. ' + 
            'To overcome this, go to Tools->Internet Options->Security->Custom Level. ' + 
            'Find the setting for "Initialize and script ActiveX controls not marked as safe" and change it to "Enable" or "Prompt"'); 
        }
}
}

function writeFileInIE(filePath, fileContent) {
try {
var fso = new ActiveXObject("Scripting.FileSystemObject");

var file = fso.OpenTextFile(filePath, 2, true);

file.WriteLine(fileContent);

    file.Close();
} catch (e) {
if (e.number == -2146827859) {
            alert('Unable to access local files due to browser security settings. ' + 
            'To overcome this, go to Tools->Internet Options->Security->Custom Level. ' + 
            'Find the setting for "Initialize and script ActiveX controls not marked as safe" and change it to "Enable" or "Prompt"'); 
        }
}
}

From:  Jacky Cui's Java Home: Read and Write local files in IE