Instructions for using the fs.appendFile method in node.js_node.js

Method description:

This method inserts data into the file asynchronously. If the file does not exist, it will be created automatically. data can be any string or cache.

Grammar:

Copy code The code is as follows:

fs.appendFile(filename, data, [options], callback)

Since this method belongs to the fs module, the fs module needs to be introduced before use (var fs = require(“fs”) )

Receive parameters:

1. filename {String}

2. data {String | Buffer}

3. options {Object}

encoding {String | Null} default = ‘utf8′

mode {Number} default = 438 (aka 0666 in Octal)

flag {String} default = ‘a’

4. callback {Function}

Example:

Copy code The code is as follows:

var fs = require("fs");
fs.appendFile('message.txt', 'data to append', function (err) {
if (err) throw err;
console.log('The "data to append" was appended to file!');
});

Source code:

Copy code The code is as follows:

fs.appendFile = function(path, data, options, callback_) {
var callback = maybeCallback(arguments[arguments.length - 1]);
if (util.isFunction(options) || !options) {
Options = { encoding: 'utf8', mode: 438 /*=0666*/, flag: 'a' };
} else if (util.isString(options)) {
options = { encoding: options, mode: 438, flag: 'a' };
} else if (!util.isObject(options)) {
Throw new TypeError('Bad arguments');
}
if (!options.flag)
Options = util._extend({ flag: 'a' }, options);
fs.writeFile(path, data, options, callback);
};