Regrettably, the keyword use does not actually exist in javascript. However, there are multiple ways to achieve the desired outcome.

Here is an example where totalPrice is a function and tax is global.

// Example provided
var tax = 10;
var totalPrice = function (quantity, price) {
    return (price * quantity) * (tax + 1.0);
};
var price = totalPrice(1, 1);
console.log ("The price is : " + price);

In my opinion, one possible solution that closely resembles the use of the keyword use is to create a function that initializes tax within a sub scope and returns a new function:

// Example 1 with returned function
function generatePriceCalculator(tax) {
    return function(quantity, price) {
        if ("undefined" === typeof tax) {
            throw "Tax is undefined";
        }

        return (price * quantity) * (tax + 1.0);
    };
};

var priceCalculator = generatePriceCalculator(20);
var price1 = priceCalculator(1, 1);
console.log ("Price for Example 1 is : " + price1);

In this scenario, the generatePriceCalculator function sets the value for tax within the returned function.

Alternatively, you can create an external function to call within the closure.

// Example 2 using a function to retrieve tax value
function getTax() {
    return 30;
}
var totalPrice2 = function (quantity, price) {
    var tax = getTax();
    return (price * quantity) * (tax + 1.0);
};
var price2 = totalPrice2(1, 1);
console.log ("Price for Example 2 is : " + price2);

You can view these examples here:

View Examples on JSFiddle

JavaScript does not have a specific keyword for accessing variables in different scopes.

In JavaScript, variables are accessible to all child scopes. For example:

(function() {
  var outerVariable = true;
  (function() {
    console.log(typeof outerVariable); // boolean
    (function() {
      console.log(typeof outerVariable); // boolean
    }())
  }());
}());

However, you cannot access variables that are defined in separate, non-parent scopes. For example:

(function() {
  var someVariable = true;
}());
(function() {
  console.log(typeof someVariable); // undefined
}());

It is important to write JavaScript code in a way that ensures access only to necessary variables. Consider the following example:

(function() {
  var math = (function() {
    // inner variable
    var PI = 3.141592653589793;

    // inner function
    function multiply(...args) {
      return args.reduce((a, b)=> a * b);
    }

    // outer functions
    return {
      circleArea: function circleArea(r) {
        return multiply(r, r, PI);
      },
      circumference: function circumference(r) {
        return multiply(2, PI, r);
      }
    };
  }());

  console.log(math.circleArea(5)); // 78.53981633974483
  console.log(math.circumference(10)); // 62.83185307179586

  console.log(typeof PI); // "undefined"
  console.log(typeof multiply); // "undefined"
}());

In this example, the IIFE creating the `math` object allows access to the `PI` variable and `multiply` function within its scope. The returned functions can also access `PI` and `multiply`, as they are inside the same IIFE. However, outside of this IIFE, `PI` and `multiply` are undefined.

For more information, see:

• How do JavaScript closures work?
• What is the purpose of wrapping whole Javascript files in anonymous functions like “(function(){ … })()”?

To connect your external variables to the this keyword within your closure, you can utilize the .bind() method:

The function bind() generates a fresh function that, whenever invoked, has its this keyword adjusted to the specified value alongside a given series of arguments coming before any provided when calling the new function.

For more information, visit https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind

If you're searching for an alternative to the use keyword in JavaScript with the intention of improving code readability, consider using window.variablename. In JavaScript, variables declared at the global scope are automatically associated with the window object. For instance:

var window.tax = 10;
var totalPrice = function (quantity, price){
    return (price * quantity) * (window.tax + 1.0);  
};

By utilizing window.variablename, it becomes evident to anyone reviewing the code that the referenced variable is part of the global scope (specifically window.tax). This approach eliminates ambiguity and enhances code transparency.

Let's clear something up from the start: JavaScript is in a league of its own, distinct from PHP and C++.

use() might not be the go-to method in JS, but fear not! There are countless ways to achieve what you need in this versatile language. In addition to the solutions provided earlier, here's another example:

var tax = 'incorrect';

var priceFactory = function(tax) { 
    // private `tax` variable specific to this scope
    var tax = tax;

    // Alternatively, implement a complex check like:
    // var tax = 'number' ==  typeof tax && tax || function() { throw "No tax provided"; }();

    return function(quantity, price) {
        return (price * quantity) * (1 + tax / 100);
    }
};

var price = new priceFactory(10); // 10% tax

var totalPrice = price(1, 100)

It seems unlikely that JS will ever fulfill your requirements. PHP enforces strict scope rules. Any variable defined within a function is confined to that specific function. Similarly, variables defined outside of a function are not automatically accessible inside the function. The use of use or global changes where and when you can utilize a variable within a certain scope.

By default, JS places everything in the global scope. It operates in a somewhat unconventional manner, where if you want to restrict a variable's scope to a specific function, you must explicitly pass it as an argument or specifically constrain its scope.

function bob(x) {
    // x is local by default
    y = 1; //global
    var z = 2; //local
}

In essence, all variables in JS are implicitly declared using use.