Java Script : Block Scope II

Block Scope II

Mari kita lihat contoh lain dari cakupan blok, sebagaimana didefinisikan dalam blok if:

const colorOfSky = () => {
  const dusk = true;
  let color = 'blue'; 
  if (dusk) {
    let color = 'pink';
    console.log(color); // pink
  }
  console.log(color); // blue 
};

colorOfSky(); // blue
console.log(color); // ReferenceError

Di sini, Anda akan melihat:

1. Kami membuat variabel  dusk di dalam fungsi colorOfSky() .
2. Setelah pernyataan if, kita mendefinisikan blok kode baru {} braces. Disini kita menetapkan nilai baru untuk variabel  color jika statemen if bernilai true.
3. Dalam blokif , variabel color memiliki nilai pink, meskipun diluar blok if , dalam badan fungsi, variabel colorbernilai  blue.

Block scope is a powerful tool in JavaScript, since it allows us to define variables with precision, and not pollute the global namespace.

1.

Remove the statement that erroneously logs the value of the lightWavesvariable to the console outside of the function block.

2.

Let's continue by adding another variable to the visibleLightWaves()function. Beneath the lightWavesvariable, using let, add a variable region and set it equal to 'The Arctic'.

3.

Beneath the region variable, create an if statement that checks if the region is the 'The Arctic'.

4.

Inside the if block, define a new variable lightWaves and set it equal to 'Northern Lights'.

5.

Beneath the variable in the if block, use console.log() to log the value of the block variable inside the if block.

Notice the ouput. Inside the if block console.log(lightWaves) logs the value Northern Lights to the console. Outside the if block, but still within the function, the same statement logs Moonlight to the console.