I've been learning about node.js and modules, and can't seem to get the Underscore library to work properly... it seems that the first time I use a function from Underscore, it overwrites the _ object with the result of my function call. Anyone know what's going on? For example, here is a session from the node.js REPL:
Admin-MacBook-Pro:test admin$ node
> require("./underscore-min")
{ [Function]
_: [Circular],
VERSION: '1.1.4',
forEach: [Function],
each: [Function],
map: [Function],
inject: [Function],
(...more functions...)
templateSettings: { evaluate: /<%([\s\S]+?)%>/g, interpolate: /<%=([\s\S]+?)%>/g },
template: [Function] }
> _.max([1,2,3])
3
> _.max([4,5,6])
TypeError: Object 3 has no method 'max'
at [object Context]:1:3
at Interface.<anonymous> (repl.js:171:22)
at Interface.emit (events.js:64:17)
at Interface._onLine (readline.js:153:10)
at Interface._line (readline.js:408:8)
at Interface._ttyWrite (readline.js:585:14)
at ReadStream.<anonymous> (readline.js:73:12)
at ReadStream.emit (events.js:81:20)
at ReadStream._emitKey (tty_posix.js:307:10)
at ReadStream.onData (tty_posix.js:70:12)
> _
3
When I make Javascript files myself and import them, they seem to be working properly. Maybe there's something special with the Underscore library?
This question is related to
node.js
module
underscore.js
The Node REPL uses the underscore variable to hold the result of the last operation, so it conflicts with the Underscore library's use of the same variable. Try something like this:
Admin-MacBook-Pro:test admin$ node
> _und = require("./underscore-min")
{ [Function]
_: [Circular],
VERSION: '1.1.4',
forEach: [Function],
each: [Function],
map: [Function],
inject: [Function],
(...more functions...)
templateSettings: { evaluate: /<%([\s\S]+?)%>/g, interpolate: /<%=([\s\S]+?)%>/g },
template: [Function] }
> _und.max([1,2,3])
3
> _und.max([4,5,6])
6
Or :
var _ = require('underscore')._;
The name _ used by the node.js REPL to hold the previous input. Choose another name.
As of today (April 30, 2012) you can use Underscore as usual on your Node.js code. Previous comments are right pointing that REPL interface (Node's command line mode) uses the "_" to hold the last result BUT on you are free to use it on your code files and it will work without a problem by doing the standard:
var _ = require('underscore');
Happy coding!
Note: The following only works for the next line of code, and only due to a coincidence.
With Lodash,
require('lodash');
_.isArray([]); // true
No var _ = require('lodash') since Lodash mysteriously sets this value globally when required.
Source: Stackoverflow.com