When your callback to readFile
executes, the for loop will already have finished. So i
will be files.length
and files[i]
will be undefined
. To mitigate this, you need to wrap the variables in a closure. The simplest way to do this is to create a function which does your readFile
call, and call that in the loop:
function read(file) { require('fs').readFile(file, 'utf8', function (error,data) { cache[file]=data; }); } for(var i = 0; i < files.length; i++){ read(files[i]); }
For even better execution control, you might want to look into async:
function readAsync(file, callback) { fs.readFile(file, 'utf8', callback); } async.map(files, readAsync, function(err, results) { // results = ['file 1 content', 'file 2 content', ...] });
Edit: Made use of helper function for async example.