What is the JavaScript convention for no operation?

Question

What is the JavaScript convention for no operation? Like a Python pass command.

• One option is simply an empty function: function() {}

Answer 1

The most concise and performant noop is an empty arrow function: ()=>{}.

Arrow functions work natively in all browsers except IE (there is a babel transform if you must):

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()=>{} vs. Function.Prototype

• ()=>{} is 87% faster than Function.prototype in Chrome 67.
• ()=>{} is 25% faster than Function.prototype in Firefox 60.
• ()=>{} is 85% faster than Function.prototype in Edge (6/15/2018).
• ()=>{} is 65% less code than Function.prototype.

The test below heats up using the arrow function to give bias to Function.prototype, yet the arrow function is the clear winner:

const noop = ()=>{};
const noopProto = Function.prototype;

function test (_noop, iterations) {
    const before = performance.now();
    for(let i = 0; i < iterations; i++) _noop();
    const after = performance.now();
    const elapsed = after - before;
    console.info(`${elapsed.toFixed(4)}MS\t${_noop.toString().replace('\n', '')}\tISNOOP? ${_noop() === undefined}`);
    return elapsed;
}

const iterations = 10000000
console.info(`noop time for ${iterations.toLocaleString()} iterations`)
const timings = {
    noop: test(noop, iterations),
    noopProto: test(noopProto, iterations)
}

const percentFaster = ((timings.noopProto - timings.noop)/timings.noopProto).toLocaleString("en-us", { style: "percent" });
console.info(`()=>{} is ${percentFaster} faster than Function.prototype in the current browser!`)