CODEWITHSUNDEEP
javascriptlodash
michel lompret
michel lompret

Reputation: 317

lodash function's prefix

I'm a noob so apologie if this question sounds stupid but why do people use _. before lodash function. I've seen people usually use _. like _.cloneDeep() for lodash function but sometimes they seem to use lodash function without anything like here. Is there a reason ?

Upvotes: 0

Views: 1208

Answers (3)

Lars Gyrup Brink Nielsen
Lars Gyrup Brink Nielsen

Reputation: 4095

It depends on the JavaScript environment you have set up. In some environments, your only option is to use the global underscore (_) object that has all the functions.

When using a run time or compile time environment that supports ES6 Modules, you can import the functions one at a time like this

import { cloneDeep } from 'lodash';

or this

import cloneDeep from 'lodash/cloneDeep';

There is even an ES6 Module for each function and other package formats as well.

import cloneDeep from 'lodash.clonedeep';

The ES6 Module options can help you make a smaller bundle for your app.

The first two samples - both of which are equivalent - rely on tree shaking to compile a smaller bundle.

In the third example we are only including the functions that we need. However, we will need to npm install --save lodash.clonedeep for each function that we want to use.

Upvotes: 1

mhodges
mhodges

Reputation: 11116

It has to do with how lodash is imported. Most of the time, people say import * as _ from lodash, so the entire library of lodash is referenced with _.

However, in the case you provided, they are just importing a single function from lodash by name (which works similarly to object destructuring - it will create a local variable with an identifier equal to that of the property name you are extracting), so there is no need for the _ prefix.

What I prefer to do is something like this:

import { find } from 'lodash';
var _ = { find };

var item = _.find(.....);

And if you're using TypeScript, the Partial comes in handy here, like so:

var _:Partial<LoDashStatic> = {find};

That way you can get intellisense/type-safety without having to import the entire lodash library. Plus, your syntax doesn't change - it's always prefixed by _.

The reason I like it prefixed is so that I can guarantee the identifiers of imports will never conflict with any local identifiers I have. Also, I can always know at a glance whether something is a lodash method or not, without having to scroll up and look at the imports for that file.

Upvotes: 0

Chris Riebschlager
Chris Riebschlager

Reputation: 1333

The key there is this line:

import { find } from 'lodash';

In that case they are "extracting" one function from lodash and assigning it to a variable find.

This is fine if you only need a function or two from lodash. But if you need several, this technique gets a little cumbersome.

Upvotes: 0

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