Why _ as variable name in node REPL mode to require failed

Question

Node version v5.4.1 and I installed lodash in current directory's node_modules. And I encouter this issue where '_' seems special.

> var _ = require('lodash');
undefined
> _.defaults
TypeError: Cannot read property 'defaults' of undefined
    at repl:1:2
    at REPLServer.defaultEval (repl.js:252:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer.<anonymous> (repl.js:417:12)
    at emitOne (events.js:82:20)
    at REPLServer.emit (events.js:169:7)
    at REPLServer.Interface._onLine (readline.js:210:10)
    at REPLServer.Interface._line (readline.js:549:8)
    at REPLServer.Interface._ttyWrite (readline.js:826:14)
> var l = require('lodash');
undefined
> l.defaults
[Function]
>

I saw a question related to undefined output. But no question yet cares about the failure of 'require' when '_' as variable name. Do you know any about it?

mscdex · Accepted Answer · 2016-09-27 13:50:22Z

1

The underscore is a special variable that holds the result of the most recent expression. Prior to node v6.0.0, this behavior could not be disabled. However, node v6.0.0 introduced a change that allowed the underscore variable to be overwritten. So you will need to upgrade your copy of node if you want to reassign the _ variable in the node REPL.

edited Sep 27, 2016 at 13:50

answered Sep 27, 2016 at 3:11

mscdex

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