ECMAScript proposal: "use slow" directive.

[DPOH-VAR]

ECMAScript proposal: The "use slow" Directive

• Motivation
• Declaring
• Usage

Motivation

"use slow"; defines that code should be executed slowly.
Basic performance decrease: x 2.

Declaring

"use slow"; Must be declared in a Directive Prologue

At the beginning of a script:

"use slow";
console.log('slow code');

At the beginning of a function:

console.log('normal');

function slowFunction(){
  "use slow";
  console.log('slow');
}

"use slow"; affects only the function in which it is declared.

Usage

Use slow can be be more than once. Slowdown effect is multiplied. Example:

"use slow"; // x 2
"use slow"; // x 2
"use slow"; // x 2
console.log('this code 8 times slower');

Use slow inside the function takes effect from the outside code or function:

"use slow"; // x 2
console.log('this code 2 times slower');

function f(){
  "use slow"; // x 2
  console.log('this code 4 times slower');
  
  return function g(){
    "use slow"; // x 2
    console.log('this code 8 times slower');
  }
}