JavaScript Pipeline Operator

The JavaScript Pipeline Operator ( |> ) is used to pipe the value of an expression into a function. This operator makes chained functions more readable. This function is called the ( |> ) operator and whatever value is used on the pipeline operator is passed as an argument to the function. The functions are placed in the order in which they operate on the argument.

Syntax:

expression |> function

Using the Pipeline Operator

As the Pipeline Operator is an experimental feature and currently in stage 1 proposal, there is no support for currently available browsers and therefore is also not included in Node. However, one can use Babel (JavaScript Compiler) to use it.

Steps:

• Before moving ahead, make sure that Node.js is installed.
• Create a directory on your desktop (say pipeline-operator) and within that directory create a JavaScript file (say main.js).
• Navigate to the directory and initialize a package.json file that contains relevant information about the project and its dependencies. 

  npm init

• Install Babel in order to use the operator. A pipeline operator is not currently part of JavaScript language, babel is used to compile the code so that it can be understood by Node.

  npm install @babel/cli @babel/core 
      @babel/plugin-proposal-pipeline-operator 

• To direct Babel about the compilation of the code properly, a file named .babelrc is created with the following lines:

  {
    "plugins": 
    [
        [
            "@ babel/plugin-proposal-pipeline-operator",
            {
                "proposal" : "minimal"
            }    
        ]
    ]
  }

• Add a start script to the package.json file which will run babel:

  "start" : "babel main.js --out-file output.js && node output.js"

• Run the code: 

  npm start

Example: This exmaple shows the use of Pipeline Operator.

Javascript

// JavaScript Code (main.js)
function add(x) {
    return x + 10;
}
function subtract(x) {
    return x - 5;
}
// Without pipeline operator
let val1 = add(subtract(add(subtract(10))));
console.log(val1);

// Using pipeline operator

// First 10 is passed as argument to subtract
// function then returned value is passed to
// add function then value we get is passed to
// subtract and then the value we get is again
// passed to add function
let val2 = 10 |> subtract |> add |> subtract |> add;
console.log(val2);

Output:

20
20