Dollar Sign Before a Variable

Why would a JavaScript variable start with a dollar sign?

Very common use in jQuery is to distinguish jQuery objects stored in variables from other variables.

For example, I would define:

var $email = $("#email"); // refers to the jQuery object representation of the dom object
var email_field = $("#email").get(0); // refers to the dom object itself

I find this to be very helpful in writing jQuery code and makes it easy to see jQuery objects which have a different set of properties.

What is the purpose of the dollar sign in JavaScript?

A '$' in a variable means nothing special to the interpreter, much like an underscore.

From what I've seen, many people using jQuery (which is what your example code looks like to me) tend to prefix variables that contain a jQuery object with a $ so that they are easily identified and not mixed up with, say, integers.

The dollar sign function $() in jQuery is a library function that is frequently used, so a short name is desirable.

What do the dollar-sign ( $ ) do before variables in Cypress (in then clauses)

Ditto comments above, but further info -

You should wait on the intercept, not get it.

cy.get('@postContentFull') will only work if the intercept has already intercepted.

Also, since you construct a new intercept for each article make the alias unique (otherwise you can't be sure which intercept you get).

cy.fixture( articleFixture, "utf8" )
  .then(article => {                // convention: no $ here, since it's not jQuery

    const alias = 'postContentFull' + article.postId
    cy.intercept('/wp-json/sn/public/v1/article/' + article.postId)
      .as(alias)

    cy.visit('/');                 // visit baseUrl
    if(userType !== 'noUser') {
      cy.loginUser(userType);
    }

    cy.visit(article.url);         // Cypress prepends baseUrl

    cy.wait('@' + alias).then(() => {

      if(article[userType].hasAccess) {
        ...
      } else {
        ...
      }

    })
  })

What is the effect of adding '$' dollar sign infront of event in Angular?

$ prefix in variable names has no any kind of an effect. A $ dollar sign in JavaScript (and TypeScript by extension) is a valid identifier to use as part of a variable name, it carries no syntactical meaning. It can be used in the beginning, middle or end of a variable/function name.

Specifically when it comes to $event and its use in Angular, it is more of a convention carried over from the days of AngularJS. In AngularJS, internal variables exposed by the framework were prefixed with a $.

That is why sometimes you see event and other times $event.

There was a proposal to get rid of it, but nothing happened.

So it is more of a question of style and conventions, and it is up to the personal/project preferences to come up with a convention about whether to use $event or event.

What does the dollar sign do in Swift / SwiftUI?

The $ is used in conjunction with property delegates.

It's not an operator, but a prefix (thanks @matt!).

For more about property delegates, see this Swift Evolution document.

e.g. in @State var aState = false, State is a property delegate.

This means that if we write:

• aState we're accessing a Bool value
• $aState we're accessing a Binding<Bool> value

Different property delegates will generate different values.

Dollar sign before a variable

To access a column, use:

my_data[ , cond]

or

my_data[[cond]]

The ith row can be accessed with:

my_data[i, ]

Combine both to obtain the desired value:

my_data[i, cond]

or

my_data[[cond]][i]

When should I use the dollar symbol ($) in a variable name?

From the Java Language Specification on identifiers:

The $ character should be used only in mechanically generated source code or, rarely, to access pre-existing names on legacy systems.

Dollar sign in front of a variable name or no dollar sign

$ has no special meaning in a JavaScript identifier.

There is a convention to use a variable name starting with a $ character to represent a variable that will hold a jQuery object.

What does ${} (dollar sign and curly braces) mean in a string in JavaScript?

You're talking about template literals.

They allow for both multiline strings and string interpolation.

Multiline strings:

console.log(`foo

bar`);

// foo

// bar