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JavaScript

Tony Shangkuan
Tony Shangkuan
7,200 Points
Posted by Tony Shangkuan
Tony Shangkuan
7,200 Points

How does value() & randomRGB(randomValue) work in this case

This is an course link

let html = '';
const randomValue = () => Math.floor(Math.random()*256);

function randomRGB(value) {
  const color = `rgb( ${value()}, ${value()}, ${value()} )`;
  return color;
}

for (let i=1; i<=10; i++) {
  html += `<div style="background-color: ${randomRGB(randomValue)}">${i}</div>`;
}

document.querySelector('main').innerHTML = html;

two questions:

  1. randomValue() is function but does not have () in randomRGB(randomValue)
  2. value is not a function but is used as a function value() in rgb( ${value()}, ${value()}, ${value()} )

1 Answer

Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

Last January, someone asked this very similar question. I'll repeat my answer here:

When randomRGB is called in the main program, the argument passed to it is randomValue, which is the name of a function. So for the duration of the randomRGB function, the parameter name "value" is equal to "randomValue", which means it can be called as a function.

When a function reference is passed as an argument to another function, this is often referred to as a "callback". And when passing a function reference, the parentheses are not used. If they were, the function would be called immediately and the return value would get passed instead.

So the value() function is created every time randomRGB is called.

Tony Shangkuan
Tony Shangkuan
7,200 Points
Tony Shangkuan
Tony Shangkuan
7,200 Points

Although I started to understand a bit better, I'm still a bit confused. Is there any course to further address the use of a function reference ?

Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

Perhaps the Callback Functions in JavaScript course is what you're looking for.