Disallow Mixed Requires (no-mixed-requires)

In the Node.JS community it is often customary to separate the required modules from other variable declarations, sometimes also grouping them by their type. This rule helps you enforce this convention.

Rule Details

When this rule is enabled, all var statements must satisfy the following conditions:


This rule comes with one boolean option called grouping which is turned off by default. You can set it in your eslint.json:

    "no-mixed-requires": [1, true]

If enabled, violations will be reported whenever a single var statement contains require declarations of mixed types (see the examples below).


This rule distinguishes between six kinds of variable declaration types:

In this document, the first four types are summed up under the term require declaration.


var fs = require('fs'),        // "core"     \
    async = require('async'),  // "module"   |- these are "require declaration"s
    foo = require('./foo'),    // "file"     |
    bar = require(getName()),  // "computed" /
    baz = 42,                  // "other"
    bam;                       // "uninitialized"


The following patterns are considered okay and do not cause warnings:

// only require declarations (grouping off)
var eventEmitter = require('events').EventEmitter,
    myUtils = require('./utils'),
    util = require('util'),
    bar = require(getBarModuleName());

// only non-require declarations
var foo = 42,
    bar = 'baz';

// always valid regardless of grouping because all declarations are of the same type
var foo = require('foo' + VERSION),
    bar = require(getBarModuleName()),
    baz = require();

The following patterns are considered warnings:

// mixing require and other declarations
var fs = require('fs'),
    i = 0;

// invalid because of mixed types "core" and "file" (grouping on)
var fs = require('fs'),
    async = require('async');

// invalid because of mixed types "file" and "unknown" (grouping on)
var foo = require('foo'),
    bar = require(getBarModuleName());

When Not To Use It

Internally, the list of core modules is retrieved via require("repl")._builtinLibs. If you use different versions of Node.JS for ESLint and your application, the list of core modules for each version may be different. The above mentioned _builtinLibs property became available in 0.8, for earlier versions a hardcoded list of module names is used as a fallback. If your version of Node is older than 0.6 that list may be inaccurate.

If you use a pattern such as UMD where the required modules are not loaded in variable declarations, this rule will obviously do nothing for you.

The implementation is not aware of any local functions with the name require that may shadow Node’s global require.


This rule was introduced in ESLint 0.0.9.