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Nodejs console overload scope issue

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[前端(javascript) 所属分类 前端(javascript) | 发布者 店小二05 | 时间 2019 | 作者 红领巾 ] 0人收藏点击收藏

I am trying to override the console in Nodejs with Winston.

for (var z in loggerSettings) { console[z] = (function () { var i = z + '' , _backup = console[z]; return function () { var utfs = arguments.length >= 2 ? util.format.apply(util, arguments) : arguments[0] , coldex = 0; if (true) logger[i == 'log' ? 'info' : i](utfs); if (loggerSettings[i].console){ if ((coldex = utfs.indexOf(']') + 1) <= MAX_TAG_LENGTH) _backup(utfs.substring(0, coldex)[i]['inverse'] + utfs.substring(coldex)); else _backup(utfs); } } })(); }

Here var z is just a the basic console.log, console.info, console.warn methods. The issue is z is changing for each of the anonymous function. It is a bit challenging to address the problem, but the scope of z seems to change and the variable z is not exactly sticking to a constant value for each iteration of the loop. Z doesn't want to stick to its scope.

Problem courtesy of: bluejamesbond

Solution

javascript has function scope, but no block scope, meaning that every reference to z in your console-functions will use the last value of z .

If you want 'z' to stick, pass it as an argument to an anonymous function:

for (var z in loggerSettings) { (function(z) { console[z] = (function () {...}); )(z); };

Solution courtesy of: robertklep

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