Call Functions with Context in JavaScript

Introduction

In this lab, we will explore how to call functions with context using a closure in JavaScript. We will learn how to pass a key and a set of arguments to a function, and then call it with the given context. Through practical examples, we will see how this technique can be used to simplify code and make it more readable.

Skills Graph

%%%%{init: {'theme':'neutral'}}%%%% flowchart RL javascript(("JavaScript")) -.-> javascript/BasicConceptsGroup(["Basic Concepts"]) javascript(("JavaScript")) -.-> javascript/AdvancedConceptsGroup(["Advanced Concepts"]) javascript(("JavaScript")) -.-> javascript/ToolsandEnvironmentGroup(["Tools and Environment"]) javascript/BasicConceptsGroup -.-> javascript/variables("Variables") javascript/BasicConceptsGroup -.-> javascript/data_types("Data Types") javascript/BasicConceptsGroup -.-> javascript/arith_ops("Arithmetic Operators") javascript/BasicConceptsGroup -.-> javascript/comp_ops("Comparison Operators") javascript/BasicConceptsGroup -.-> javascript/array_methods("Array Methods") javascript/AdvancedConceptsGroup -.-> javascript/async_prog("Asynchronous Programming") javascript/AdvancedConceptsGroup -.-> javascript/higher_funcs("Higher-Order Functions") javascript/AdvancedConceptsGroup -.-> javascript/spread_rest("Spread and Rest Operators") javascript/ToolsandEnvironmentGroup -.-> javascript/debugging("Debugging") subgraph Lab Skills javascript/variables -.-> lab-28185{{"Call Functions with Context"}} javascript/data_types -.-> lab-28185{{"Call Functions with Context"}} javascript/arith_ops -.-> lab-28185{{"Call Functions with Context"}} javascript/comp_ops -.-> lab-28185{{"Call Functions with Context"}} javascript/array_methods -.-> lab-28185{{"Call Functions with Context"}} javascript/async_prog -.-> lab-28185{{"Call Functions with Context"}} javascript/higher_funcs -.-> lab-28185{{"Call Functions with Context"}} javascript/spread_rest -.-> lab-28185{{"Call Functions with Context"}} javascript/debugging -.-> lab-28185{{"Call Functions with Context"}} end

How to Call Functions with Context in JavaScript

To execute code in Node.js, open the Terminal/SSH and type node. If you want to call a function with a specific context and a set of arguments in JavaScript, you can use a closure. Here's how you can do it:

Define a function called call that takes a key and a set of args as parameters and returns a new function that takes a context parameter.

const call =
  (key, ...args) =>
  (context) =>
    context[key](...args);

Use the call function to call the map function on an array of numbers. In this example, the map function doubles each number in the array.

Promise.resolve([1, 2, 3])
  .then(call("map", (x) => 2 * x))
  .then(console.log); // [ 2, 4, 6 ]

You can also bind the call function to a specific key, such as map, and use it to call the map function on an array of numbers.

const map = call.bind(null, "map");
Promise.resolve([1, 2, 3])
  .then(map((x) => 2 * x))
  .then(console.log); // [ 2, 4, 6 ]

By using the call function, you can easily call any function with a specific context and set of arguments.

Summary

Congratulations! You have completed the Call Functions With Context lab. You can practice more labs in LabEx to improve your skills.