Underscore in JavaScript

Question

What does the underscore after "state.triggeredTests =" mean:

mutations: {

setTriggeredTest(state, data) {

  state.triggeredTests = _
    .chain(data)
    .forEach((item) => {
      item.dateFormatted = moment(item.date).format('DD MMMM YYYY');
      item.explanationTest = testMapping.get(item.test);
    })
    // .sortedUniqBy('explanationTest')
    .orderBy('date')
    .groupBy('date')
    .value();
},

Rikin · Accepted Answer · 2018-10-03 19:49:39Z

3

Its a library of function/utilities/helpers which generally can be either lodash or underscore

answered Oct 3, 2018 at 19:49

Rikin

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2 Comments

Alexey Starinsky Over a year ago

so, it is something like a namespace in C++ ?

Rikin Over a year ago

Sort of, _ is a valid variable declaration allowed in Javascript, so libraries like underscore or lodash just use that declaration using var _ = (function() {...})(); to point to their public functions which are available to you and which may or may not be chainable depending on library. Similar example is $ declaration which usually people identify as jQuery or Prototype library.

gaperton · Accepted Answer · 2018-10-03 19:56:42Z

3

_ is the completely valid identifier in JS. _ global variable is being traditionally used by the underscore library and its clones as a namespace.

P.S.: $ is the valid identifier as well, and it's being used by jQuery or similar libraries.

edited Oct 3, 2018 at 19:56

answered Oct 3, 2018 at 19:52

gaperton

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1 Comment

Tyler Roper Over a year ago

Worth noting that OP's example is actually lodash as opposed to underscore, AFAICT.

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